Devices and methods for high voltage and solar applications

ABSTRACT

Provided herein are devices comprising one or more cells, and methods for fabrication thereof. The devices may be electrochemical devices. The devices may include three-dimensional supercapacitors. The devices may be microdevices such as, for example, microsupercapacitors. In some embodiments, the devices are three-dimensional hybrid microsupercapacitors. The devices may be configured for high voltage applications. In some embodiments, the devices are high voltage microsupercapacitors. In certain embodiments, the devices are high voltage asymmetric microsupercapacitors. In some embodiments, the devices are integrated microsupercapacitors for high voltage applications.

CROSS-REFERENCE

This application claims the benefit of U.S. Provisional Application No.62/312,408 filed Mar. 23, 2016, and U.S. Provisional Application No.62/421,920 filed Nov. 14, 2016, which applications are incorporatedherein in their entirety by reference.

BACKGROUND

As a result of the rapidly growing energy needs of modern life, thedevelopment of high performance energy storage devices has gainedsignificant attention.

Supercapacitors are promising energy storage devices with propertiesintermediate between those of batteries and traditional capacitors, butthey are being improved more rapidly than either. Over the past coupleof decades, supercapacitors have become key components of everydayproducts by replacing batteries and capacitors in an increasing numberof applications. Their high power density and excellent low temperatureperformance have made them the technology of choice for application inback-up power, cold starting, flash cameras, regenerative braking, andhybrid electric vehicles. The future growth of this technology dependson further improvements in many areas, including energy density, powerdensity, calendar life, cycle life, and production cost.

SUMMARY

The instant inventors have recognized a need for improved design andintegration of hybrid materials into microsupercapacitors (e.g., due tocomplicated microfabrication techniques that may involve building 3Dmicroelectrodes with micrometer separations).

The present disclosure provides a simple, yet versatile, technique forthe fabrication of microdevices such as, for example, 3D hybridmicrosupercapacitors. In some embodiments, such 3D hybridmicrosupercapacitors are based on interconnected corrugated carbon-basednetwork (ICCN) and MnO₂. In some embodiments, the microdevices hereinenable a capacitance per footprint (e.g., an ultrahigh capacitance perfootprint) approaching about 400 mF/cm². In some embodiments,microdevices herein provide an energy density of up to about 22 Wh/L(e.g., more than two times that of lithium thin film batteries). Thesedevelopments are promising, among other examples, for microelectronicdevices such as biomedical sensors and radio frequency identification(RFID) tags (e.g., where high capacity per footprint is crucial).

The present disclosure provides a method for the preparation and/orintegration of microdevices for high voltage applications. In someembodiments, the present disclosure provides a method for the directpreparation and integration of asymmetric microsupercapacitors for highvoltage applications. The microsupercapacitors may comprise an array ofseparate electrochemical cells. In some embodiments, the array ofseparate electrochemical cells can be directly fabricated in the sameplane and in one step. This configuration may provide very good controlover the voltage and current output. In some embodiments, the array canbe integrated with solar cells for efficient solar energy harvesting andstorage. In some embodiments, the devices are integratedmicrosupercapacitors for high voltage applications. In certainembodiments, the devices are asymmetric microsupercapacitors for highvoltage applications (high voltage asymmetric microsupercapacitors). Insome embodiments, the array comprises one or more electrochemical cellswith at least one ICCN/MnO₂ hybrid electrode.

An aspect of the present disclosure provides an approach for fabricationof hybrid laser-scribed graphene (LSG)-MnO₂ 3D supercapacitors andmicrosupercapacitors. In some embodiments, the supercapacitors and/ormicrosupercapacitors can be compact, reliable, energy dense, or anycombination thereof. In other embodiments, the supercapacitors and/ormicrosupercapacitors can charge quickly, possess long lifetime, or anycombination thereof. Given the use of MnO₂ in alkaline batteries(selling approximately 10 billion units per year) and the scalability ofgraphene-based materials, graphene/MnO₂ hybrid electrodes may offerpromise for real world applications.

An aspect of the present disclosure provides an electrochemical systemcomprising a plurality of interconnected electrochemical cells, eachelectrochemical cell comprising a first electrode and a secondelectrode, wherein at least one of the first electrode and the secondelectrode comprises an interconnected corrugated carbon-based network(ICCN). In some embodiments, the electrochemical system is capable ofoutputting a voltage of about 5 V to about 500 V. In some embodiments,the electrochemical system is capable of outputting a voltage of atleast about 5 V. In some embodiments, the electrochemical system iscapable of outputting a voltage of at least about 100 V. In someembodiments, the electrochemical system is capable of outputting avoltage of about 5 V to about 10 V, about 5 V to about 50 V, about 5 Vto about 100 V, about 5 V to about 200 V, about 5 V to about 300 V,about 5 V to about 400 V, about 5 V to about 500 V, about 10 V to about50 V, about 10 V to about 100 V, about 10 V to about 200 V, about 10 Vto about 300 V, about 10 V to about 400 V, about 10 V to about 500 V,about 50 V to about 100 V, about 50 V to about 200 V, about 50 V toabout 300 V, about 50 V to about 400 V, about 50 V to about 500 V, about100 V to about 200 V, about 100 V to about 300 V, about 100 V to about400 V, about 100 V to about 500 V, about 200 V to about 300 V, about 200V to about 400 V, about 200 V to about 500 V, about 300 V to about 400V, about 300 V to about 500 V, or about 400 V to about 500 V.

In some embodiments, the plurality of interconnected electrochemicalcells comprises at least one hybrid supercapacitor cell. In someembodiments, the plurality of interconnected electrochemical cells is anarray of hybrid microsupercapacitors. In some embodiments, the pluralityof interconnected electrochemical cells is an array ofmicrosupercapacitors fabricated by light scribing.

In some embodiments, the electrochemical system further comprises anelectrolyte disposed between the first electrode and the secondelectrode. In some embodiments, the electrolyte is an aqueouselectrolyte. In some embodiments, the system further comprises a solarcell in electrical communication with the plurality of interconnectedelectrochemical cells. In some embodiments, the solar cell is a copperindium gallium selenide (CIGS) cell or an organic photovoltaic cell.

In some embodiments, the electrochemical system comprises a planar arrayof interconnected electrochemical cells, wherein each electrochemicalcell comprises at least two electrodes, wherein each electrode comprisesa carbonaceous material, wherein at least one electrode furthercomprises a pseudocapacitive material. In some embodiments, thecarbonaceous material comprises an interconnected corrugatedcarbon-based network (ICCN), a laser scribed graphene (LSG) or anycombination thereof. In some embodiments, each electrochemical cellcomprises two electrodes, and wherein each electrode comprises acarbonaceous material and a pseudocapacitive material. In someembodiments, the pseudocapacitive material comprises MnO₂, RuO₂, Co₃O₄,NiO, Fe₂O₃, CuO, MoO₃, V₂O₅, Ni(OH)₂, or any combination thereof. Insome embodiments, the array of electrochemical cells is arranged in aninterdigitated structure. In some embodiments, the electrochemicalsystem further comprises an electrolyte disposed between the firstelectrode and the second electrode. In some embodiments, theelectrochemical system further comprises a current collector attached toan electrode. In some embodiments, at least one electrochemical cell iscapable of outputting a voltage of at least about 5 volts. In someembodiments, the electrochemical system is capable of outputting avoltage of at least 100 volts. In some embodiments, an electrochemicalcell has an energy density of at least about 22 watt-hours per liter(Wh/L). In some embodiments, the array of electrochemical cells has acapacitance per footprint of at least about 380 millifarads per squarecentimeter (mF/cm²). In some embodiments, the array of electrochemicalcells has a volumetric capacitance of at least about 1,100 farads percubic centimeter (F/cm³).

Another aspect of the present disclosure provides a supercapacitorcomprising an array of supercapacitor cells. In some embodiments, thearray of supercapacitor cells comprises at least one hybridsupercapacitor cell. In some embodiments, the array of supercapacitorcells is an array of hybrid supercapacitor cells.

In some embodiments, the array of supercapacitor cells is capable ofoutputting a voltage of about 5 V to about 100 V. In some embodiments,the array of supercapacitor cells is capable of outputting a voltage ofat least about 5 V. In some embodiments, the array of supercapacitorcells is capable of outputting a voltage of about 5 V to about 10 V,about 5 V to about 20 V, about 5 V to about 30 V, about 5 V to about 40V, about 5 V to about 50 V, about 5 V to about 60 V, about 5 V to about70 V, about 5 V to about 80 V, about 5 V to about 90 V, about 5 V toabout 100 V, about 10 V to about 20 V, about 10 V to about 30 V, about10 V to about 40 V, about 10 V to about 50 V, about 10 V to about 60 V,about 10 V to about 70 V, about 10 V to about 80 V, about 10 V to about90 V, about 10 V to about 100 V, about 20 V to about 30 V, about 20 V toabout 40 V, about 20 V to about 50 V, about 20 V to about 60 V, about 20V to about 70 V, about 20 V to about 80 V, about 20 V to about 90 V,about 20 V to about 100 V, about 30 V to about 40 V, about 30 V to about50 V, about 30 V to about 60 V, about 30 V to about 70 V, about 30 V toabout 80 V, about 30 V to about 90 V, about 30 V to about 100 V, about40 V to about 50 V, about 40 V to about 60 V, about 40 V to about 70 V,about 40 V to about 80 V, about 40 V to about 90 V, about 40 V to about100 V, about 50 V to about 60 V, about 50 V to about 70 V, about 50 V toabout 80 V, about 50 V to about 90 V, about 50 V to about 100 V, about60 V to about 70 V, about 60 V to about 80 V, about 60 V to about 90 V,about 60 V to about 100 V, about 70 V to about 80 V, about 70 V to about90 V, about 70 V to about 100 V, about 80 V to about 90 V, about 80 V toabout 100 V, or about 90 V to about 100 V.

In some embodiments, the supercapacitor has an energy density of about10 Wh/L to about 80 Wh/L. In some embodiments, the supercapacitor has anenergy density of at least about 10 Wh/L. In some embodiments, thesupercapacitor has an energy density of about 10 Wh/L to about 20 Wh/L,about 10 Wh/L to about 30 Wh/L, about 10 Wh/L to about 40 Wh/L, about 10Wh/L to about 50 Wh/L, about 10 Wh/L to about 60 Wh/L, about 10 Wh/L toabout 70 Wh/L, about 10 Wh/L to about 80 Wh/L, about 20 Wh/L to about 30Wh/L, about 20 Wh/L to about 40 Wh/L, about 20 Wh/L to about 50 Wh/L,about 20 Wh/L to about 60 Wh/L, about 20 Wh/L to about 70 Wh/L, about 20Wh/L to about 80 Wh/L, about 30 Wh/L to about 40 Wh/L, about 30 Wh/L toabout 50 Wh/L, about 30 Wh/L to about 60 Wh/L, about 30 Wh/L to about 70Wh/L, about 30 Wh/L to about 80 Wh/L, about 40 Wh/L to about 50 Wh/L,about 40 Wh/L to about 60 Wh/L, about 40 Wh/L to about 70 Wh/L, about 40Wh/L to about 80 Wh/L, about 50 Wh/L to about 60 Wh/L, about 50 Wh/L toabout 70 Wh/L, about 50 Wh/L to about 80 Wh/L, about 60 Wh/L to about 70Wh/L, about 60 Wh/L to about 80 Wh/L, or about 70 Wh/L to about 80 Wh/L.

In some embodiments, the at least one supercapacitor cell has an energydensity at least about 6 times greater than an energy density of acarbon-based non-hybrid supercapacitor cell. In some embodiments, the atleast one hybrid supercapacitor cell comprises at least one electrodecomprising (i) a carbonaceous material and (ii) a pseudocapacitive metalor metal oxide material. In some embodiments, the at least one hybridsupercapacitor cell comprises at least one electrode comprising aninterconnected corrugated carbon-based network (ICCN) and MnO₂. In someembodiments, the at least one hybrid supercapacitor cell comprisessymmetric or asymmetric electrodes.

In some embodiments, the array of supercapacitor cells is arranged in aninterdigitated structure. In some embodiments, the array ofsupercapacitors has a capacitance per footprint of about 250 mF/cm² toabout 600 mF/cm². In some embodiments, the array of supercapacitors hasa capacitance per footprint of at least about 250 mF/cm². In someembodiments, the array of supercapacitors has a capacitance perfootprint of about 250 mF/cm² to about 300 mF/cm², about 250 mF/cm² toabout 350 mF/cm², about 250 mF/cm² to about 400 mF/cm², about 250 mF/cm²to about 450 mF/cm², about 250 mF/cm² to about 500 mF/cm², about 250mF/cm² to about 550 mF/cm², about 250 mF/cm² to about 600 mF/cm², about300 mF/cm² to about 350 mF/cm², about 300 mF/cm² to about 400 mF/cm²,about 300 mF/cm² to about 450 mF/cm², about 300 mF/cm² to about 500mF/cm², about 300 mF/cm² to about 550 mF/cm², about 300 mF/cm² to about600 mF/cm², about 350 mF/cm² to about 400 mF/cm², about 350 mF/cm² toabout 450 mF/cm², about 350 mF/cm² to about 500 mF/cm², about 350 mF/cm²to about 550 mF/cm², about 350 mF/cm² to about 600 mF/cm², about 400mF/cm² to about 450 mF/cm², about 400 mF/cm² to about 500 mF/cm², about400 mF/cm² to about 550 mF/cm², about 400 mF/cm² to about 600 mF/cm²,about 450 mF/cm² to about 500 mF/cm², about 450 mF/cm² to about 550mF/cm², about 450 mF/cm² to about 600 mF/cm², about 500 mF/cm² to about550 mF/cm², about 500 mF/cm² to about 600 mF/cm², or about 550 mF/cm² toabout 600 mF/cm².

In some embodiments, the array of supercapacitors maintains thecapacitance even at high charge-discharge rates. In some embodiments,the array of supercapacitors maintains the capacitance at acharge-discharge rate corresponding to a current density of about 5,000mA/cm³ to about 20,000 mA/cm³. In some embodiments, the array ofsupercapacitors maintains the capacitance at a charge-discharge ratecorresponding to a current density of at least about 5,000 mA/cm³. Insome embodiments, the array of supercapacitors maintains the capacitanceat a charge-discharge rate corresponding to a current density of about5,000 mA/cm³ to about 7,500 mA/cm³, about 5,000 mA/cm³ to about 10,000mA/cm³, about 5,000 mA/cm³ to about 12,500 mA/cm³, about 5,000 mA/cm³ toabout 15,000 mA/cm³, about 5,000 mA/cm³ to about 17,500 mA/cm³, about5,000 mA/cm³ to about 20,000 mA/cm³, about 7,500 mA/cm³ to about 10,000mA/cm³, about 7,500 mA/cm³ to about 12,500 mA/cm³, about 7,500 mA/cm³ toabout 15,000 mA/cm³, about 7,500 mA/cm³ to about 17,500 mA/cm³, about7,500 mA/cm³ to about 20,000 mA/cm³, about 10,000 mA/cm³ to about 12,500mA/cm³, about 10,000 mA/cm³ to about 15,000 mA/cm³, about 10,000 mA/cm³to about 17,500 mA/cm³, about 10,000 mA/cm³ to about 20,000 mA/cm³,about 12,500 mA/cm³ to about 15,000 mA/cm³, about 12,500 mA/cm³ to about17,500 mA/cm³, about 12,500 mA/cm³ to about 20,000 mA/cm³, about 15,000mA/cm³ to about 17,500 mA/cm³, about 15,000 mA/cm³ to about 20,000mA/cm³, or about 17,500 mA/cm³ to about 20,000 mA/cm³.

In some embodiments, the array of supercapacitors maintains thecapacitance at a charge-discharge rate corresponding to a scan rate ofabout 5,000 mV/s to about 20,000 mV/s. In some embodiments, the array ofsupercapacitors maintains the capacitance at a charge-discharge ratecorresponding to a scan rate of at least about 5,000 mV/s. In someembodiments, the array of supercapacitors maintains the capacitance at acharge-discharge rate corresponding to a scan rate of about 5,000 mV/sto about 6,250 mV/s, about 5,000 mV/s to about 7,500 mV/s, about 5,000mV/s to about 10,000 mV/s, about 5,000 mV/s to about 11,250 mV/s, about5,000 mV/s to about 12,500 mV/s, about 5,000 mV/s to about 15,000 mV/s,about 5,000 mV/s to about 16,250 mV/s, about 5,000 mV/s to about 17,500mV/s, about 5,000 mV/s to about 20,000 mV/s, about 6,250 mV/s to about7,500 mV/s, about 6,250 mV/s to about 10,000 mV/s, about 6,250 mV/s toabout 11,250 mV/s, about 6,250 mV/s to about 12,500 mV/s, about 6,250mV/s to about 15,000 mV/s, about 6,250 mV/s to about 16,250 mV/s, about6,250 mV/s to about 17,500 mV/s, about 6,250 mV/s to about 20,000 mV/s,about 7,500 mV/s to about 10,000 mV/s, about 7,500 mV/s to about 11,250mV/s, about 7,500 mV/s to about 12,500 mV/s, about 7,500 mV/s to about15,000 mV/s, about 7,500 mV/s to about 16,250 mV/s, about 7,500 mV/s toabout 17,500 mV/s, about 7,500 mV/s to about 20,000 mV/s, about 10,000mV/s to about 11,250 mV/s, about 10,000 mV/s to about 12,500 mV/s, about10,000 mV/s to about 15,000 mV/s, about 10,000 mV/s to about 16,250mV/s, about 10,000 mV/s to about 17,500 mV/s, about 10,000 mV/s to about20,000 mV/s, about 11,250 mV/s to about 12,500 mV/s, about 11,250 mV/sto about 15,000 mV/s, about 11,250 mV/s to about 16,250 mV/s, about11,250 mV/s to about 17,500 mV/s, about 11,250 mV/s to about 20,000mV/s, about 12,500 mV/s to about 15,000 mV/s, about 12,500 mV/s to about16,250 mV/s, about 12,500 mV/s to about 17,500 mV/s, about 12,500 mV/sto about 20,000 mV/s, about 15,000 mV/s to about 16,250 mV/s, about15,000 mV/s to about 17,500 mV/s, about 15,000 mV/s to about 20,000mV/s, about 16,250 mV/s to about 17,500 mV/s, about 16,250 mV/s to about20,000 mV/s, or about 17,500 mV/s to about 20,000 mV/s.

Some aspects provide a system comprising the supercapacitor, wherein thearray of supercapacitor cells is in electrical communication with atleast one solar cell, and wherein the at least one solar cell includes acopper indium gallium selenide (CIGS) cell, an organic photovoltaiccell, or a combination thereof.

Another aspect of the present disclosure provides a method forfabricating a supercapacitor comprising forming electrodes comprisinglaser scribing. In some embodiments, the method comprises formingelectrodes comprising LightScribe writing on a film, wherein at leastone of the electrodes is configured to store charge via one or morenon-Faradaic processes, wherein at least one of the electrodes comprisesa pseudocapacitive material configured to store charge via one or moreFaradaic processes.

In some embodiments, the supercapacitor is capable of outputting avoltage of about 5 V to about 100 V. In some embodiments, thesupercapacitor is capable of outputting a voltage of at least about 5 V.In some embodiments, the supercapacitor is capable of outputting avoltage of about 5 V to about 10 V, about 5 V to about 20 V, about 5 Vto about 30 V, about 5 V to about 40 V, about 5 V to about 50 V, about 5V to about 60 V, about 5 V to about 70 V, about 5 V to about 80 V, about5 V to about 90 V, about 5 V to about 100 V, about 10 V to about 20 V,about 10 V to about 30 V, about 10 V to about 40 V, about 10 V to about50 V, about 10 V to about 60 V, about 10 V to about 70 V, about 10 V toabout 80 V, about 10 V to about 90 V, about 10 V to about 100 V, about20 V to about 30 V, about 20 V to about 40 V, about 20 V to about 50 V,about 20 V to about 60 V, about 20 V to about 70 V, about 20 V to about80 V, about 20 V to about 90 V, about 20 V to about 100 V, about 30 V toabout 40 V, about 30 V to about 50 V, about 30 V to about 60 V, about 30V to about 70 V, about 30 V to about 80 V, about 30 V to about 90 V,about 30 V to about 100 V, about 40 V to about 50 V, about 40 V to about60 V, about 40 V to about 70 V, about 40 V to about 80 V, about 40 V toabout 90 V, about 40 V to about 100 V, about 50 V to about 60 V, about50 V to about 70 V, about 50 V to about 80 V, about 50 V to about 90 V,about 50 V to about 100 V, about 60 V to about 70 V, about 60 V to about80 V, about 60 V to about 90 V, about 60 V to about 100 V, about 70 V toabout 80 V, about 70 V to about 90 V, about 70 V to about 100 V, about80 V to about 90 V, about 80 V to about 100 V, or about 90 V to about100 V.

In some embodiments, the method further comprises selectivelyelectrodepositing the pseudocapacitive material on at least one of theelectrodes. In some embodiments, the method further comprises formingthe electrodes by laser scribing graphite oxide films. In someembodiments, the method further comprises forming a porousinterconnected corrugated carbon-based network (ICCN), wherein theporous ICCN comprises a plurality of carbon layers that areinterconnected and expanded apart from one another to form a pluralityof pores. In some embodiments, the method further compriseselectrodepositing metallic nanoparticles within the plurality of pores.In some embodiments, the method further comprises forming the electrodesin an interdigitated pattern. In some embodiments, the pseudocapacitivematerial comprises MnO₂ nanoflowers. In some embodiments, asupercapacitor cell comprises (i) a first electrode comprising an ICCNand the pseudocapacitive material and (ii) a second electrode comprisingthe ICCN, thereby forming a supercapacitor cell with asymmetricelectrodes. In some embodiments, a supercapacitor cell comprises (i) afirst electrode comprising an ICCN and the pseudocapacitive material and(ii) a second electrode comprising the ICCN and the pseudocapacitivematerial, thereby forming a supercapacitor cell with symmetricelectrodes. In some embodiments, the method further comprises directlyfabricating an array of separate supercapacitor cells in the same planeand in one step.

In some embodiments, a method for fabricating an electrochemical system,comprises: forming a carbonaceous film; forming a carbonaceous frameworkfrom the carbonaceous film; patterning the carbonaceous framework toform a planar array of two or more cells, wherein each cell comprises atleast two electrodes, and electrodepositing a pseudocapacitive materialonto a portion of the planar array. In some embodiments, thecarbonaceous film comprises graphene oxide (GO). In some embodiments,the carbonaceous film comprises a three dimensional carbon frameworkcomprising an interconnected corrugated carbon-based network (ICCN), alaser scribed graphene (LSG), or any combination thereof. In someembodiments, the forming of the carbonaceous framework from thecarbonaceous film comprises light scribing. In some embodiments, thepatterning the carbonaceous framework comprises light scribing. In someembodiments, the patterning the carbonaceous framework forms two or moreinterdigitated electrodes. In some embodiments, the array is a planararray. In some embodiments, the pseudocapacitive material comprisesMnO₂, RuO₂, Co₃O₄, NiO, Fe₂O₃, CuO, MoO₃, V₂O₅, Ni(OH)₂, or anycombination thereof. Some embodiments further comprise depositing anelectrolyte on the carbonaceous framework. Some embodiments furthercomprise connecting the two or more cells.

In some embodiments, the laser scribing is performed by a LightScribeDVD labeler through direct writing. In some embodiments, the lightscribing is performed by a light beam whose frequency is about 1×10⁸ MHzto about 18×10⁸ MHz.

In some embodiments, the light scribing is performed by a light beamwhose wavelength is about 350 nanometers (nm) to about 1,450 nanometers.In some embodiments, the light scribing is performed by a light whosewavelength is at least about 350 nanometers. In some embodiments, thelight scribing is performed by a light whose wavelength is at most about1,450 nanometers. In some embodiments, the light scribing is performedby a light whose wavelength is about 350 nanometers to about 450nanometers, about 350 nanometers to about 550 nanometers, about 350nanometers to about 650 nanometers, about 350 nanometers to about 750nanometers, about 350 nanometers to about 850 nanometers, about 350nanometers to about 950 nanometers, about 350 nanometers to about 1,050nanometers, about 350 nanometers to about 1,150 nanometers, about 350nanometers to about 1,250 nanometers, about 350 nanometers to about1,350 nanometers, about 350 nanometers to about 1,450 nanometers, about450 nanometers to about 550 nanometers, about 450 nanometers to about650 nanometers, about 450 nanometers to about 750 nanometers, about 450nanometers to about 850 nanometers, about 450 nanometers to about 950nanometers, about 450 nanometers to about 1,050 nanometers, about 450nanometers to about 1,150 nanometers, about 450 nanometers to about1,250 nanometers, about 450 nanometers to about 1,350 nanometers, about450 nanometers to about 1,450 nanometers, about 550 nanometers to about650 nanometers, about 550 nanometers to about 750 nanometers, about 550nanometers to about 850 nanometers, about 550 nanometers to about 950nanometers, about 550 nanometers to about 1,050 nanometers, about 550nanometers to about 1,150 nanometers, about 550 nanometers to about1,250 nanometers, about 550 nanometers to about 1,350 nanometers, about550 nanometers to about 1,450 nanometers, about 650 nanometers to about750 nanometers, about 650 nanometers to about 850 nanometers, about 650nanometers to about 950 nanometers, about 650 nanometers to about 1,050nanometers, about 650 nanometers to about 1,150 nanometers, about 650nanometers to about 1,250 nanometers, about 650 nanometers to about1,350 nanometers, about 650 nanometers to about 1,450 nanometers, about750 nanometers to about 850 nanometers, about 750 nanometers to about950 nanometers, about 750 nanometers to about 1,050 nanometers, about750 nanometers to about 1,150 nanometers, about 750 nanometers to about1,250 nanometers, about 750 nanometers to about 1,350 nanometers, about750 nanometers to about 1,450 nanometers, about 850 nanometers to about950 nanometers, about 850 nanometers to about 1,050 nanometers, about850 nanometers to about 1,150 nanometers, about 850 nanometers to about1,250 nanometers, about 850 nanometers to about 1,350 nanometers, about850 nanometers to about 1,450 nanometers, about 950 nanometers to about1,050 nanometers, about 950 nanometers to about 1,150 nanometers, about950 nanometers to about 1,250 nanometers, about 950 nanometers to about1,350 nanometers, about 950 nanometers to about 1,450 nanometers, about1,050 nanometers to about 1,150 nanometers, about 1,050 nanometers toabout 1,250 nanometers, about 1,050 nanometers to about 1,350nanometers, about 1,050 nanometers to about 1,450 nanometers, about1,150 nanometers to about 1,250 nanometers, about 1,150 nanometers toabout 1,350 nanometers, about 1,150 nanometers to about 1,450nanometers, about 1,250 nanometers to about 1,350 nanometers, about1,250 nanometers to about 1,450 nanometers, or about 1,350 nanometers toabout 1,450 nanometers.

In some embodiments, the light scribing is performed by a light beamwhose power is about 20 milliwatts (mW) to about 80 mW. In someembodiments, the light scribing is performed by a light whose power isat least about 20 mW. In some embodiments, the light scribing isperformed by a light whose power is at most about 80 mW. In someembodiments, the light scribing is performed by a light whose power isabout 20 mW to about 30 mW, about 20 mW to about 40 mW, about 20 mW toabout 50 mW, about 20 mW to about 60 mW, about 20 mW to about 70 mW,about 20 mW to about 80 mW, about 30 mW to about 40 mW, about 30 mW toabout 50 mW, about 30 mW to about 60 mW, about 30 mW to about 70 mW,about 30 mW to about 80 mW, about 40 mW to about 50 mW, about 40 mW toabout 60 mW, about 40 mW to about 70 mW, about 40 mW to about 80 mW,about 50 mW to about 60 mW, about 50 mW to about 70 mW, about 50 mW toabout 80 mW, about 60 mW to about 70 mW, about 60 mW to about 80 mW, orabout 70 mW to about 80 mW.

In some embodiments, the supercapacitor is a three-dimensional hybridmicrosupercapacitor. In some embodiments, the supercapacitor comprisesthree-dimensional interdigitated microsupercapacitors. In someembodiments, the supercapacitor comprises asymmetricmicrosupercapacitors. In some embodiments, the method further comprisesforming a plurality of interdigitated electrodes into an array ofmicrosupercapacitors. In some embodiments, the method further comprisesintegrating the array of microsupercapacitors with one or more solarcells.

In some embodiments, the one or more solar cells include a copper indiumgallium selenide (CIGS) cell. In some embodiments, the one or more solarcells include an organic photovoltaic cell. In some embodiments, theplurality of interdigitated electrodes is configured to store charge viaone or more non-Faradaic processes.

In some embodiments, the supercapacitor has a capacitance per footprintthat is at least about 2 times greater than a commercial carbonsupercapacitor. In some embodiments, the supercapacitor has acapacitance per footprint of about 0.3 F/cm² to about 0.8 F/cm². In someembodiments, the supercapacitor has a capacitance per footprint of atleast about 0.3 F/cm². In some embodiments, the supercapacitor has acapacitance per footprint of about 0.3 F/cm² to about 0.4 F/cm², about0.3 F/cm² to about 0.5 F/cm², about 0.3 F/cm² to about 0.6 F/cm², about0.3 F/cm² to about 0.7 F/cm², about 0.3 F/cm² to about 0.8 F/cm², about0.4 F/cm² to about 0.5 F/cm², about 0.4 F/cm² to about 0.6 F/cm², about0.4 F/cm² to about 0.7 F/cm², about 0.4 F/cm² to about 0.8 F/cm², about0.5 F/cm² to about 0.6 F/cm², about 0.5 F/cm² to about 0.7 F/cm², about0.5 F/cm² to about 0.8 F/cm², about 0.6 F/cm² to about 0.7 F/cm², about0.6 F/cm² to about 0.8 F/cm², or about 0.7 F/cm² to about 0.8 F/cm².

In some embodiments, at least one of the electrodes is a hybridelectrode that comprises the pseudocapacitive material and is configuredto store charge via the one or more non-Faradaic processes.

In some embodiments, the hybrid electrode has a volumetric capacitanceof about 500 F/cm³ to about 2,000 F/cm³. In some embodiments, the hybridelectrode has a volumetric capacitance of at least about 500 F/cm³. Insome embodiments, the hybrid electrode has a volumetric capacitance ofabout 500 F/cm³ to about 625 F/cm³, about 500 F/cm³ to about 750 F/cm³,about 500 F/cm³ to about 1,000 F/cm³, about 500 F/cm³ to about 1,125F/cm³, about 500 F/cm³ to about 1,250 F/cm³, about 500 F/cm³ to about1,500 F/cm³, about 500 F/cm³ to about 1,625 F/cm³, about 500 F/cm³ toabout 1,750 F/cm³, about 500 F/cm³ to about 2,000 F/cm³, about 625 F/cm³to about 750 F/cm³, about 625 F/cm³ to about 1,000 F/cm³, about 625F/cm³ to about 1,125 F/cm³, about 625 F/cm³ to about 1,250 F/cm³, about625 F/cm³ to about 1,500 F/cm³, about 625 F/cm³ to about 1,625 F/cm³,about 625 F/cm³ to about 1,750 F/cm³, about 625 F/cm³ to about 2,000F/cm³, about 750 F/cm³ to about 1,000 F/cm³, about 750 F/cm³ to about1,125 F/cm³, about 750 F/cm³ to about 1,250 F/cm³, about 750 F/cm³ toabout 1,500 F/cm³, about 750 F/cm³ to about 1,625 F/cm³, about 750 F/cm³to about 1,750 F/cm³, about 750 F/cm³ to about 2,000 F/cm³, about 1,000F/cm³ to about 1,125 F/cm³, about 1,000 F/cm³ to about 1,250 F/cm³,about 1,000 F/cm³ to about 1,500 F/cm³, about 1,000 F/cm³ to about 1,625F/cm³, about 1,000 F/cm³ to about 1,750 F/cm³, about 1,000 F/cm³ toabout 2,000 F/cm³, about 1,125 F/cm³ to about 1,250 F/cm³, about 1,125F/cm³ to about 1,500 F/cm³, about 1,125 F/cm³ to about 1,625 F/cm³,about 1,125 F/cm³ to about 1,750 F/cm³, about 1,125 F/cm³ to about 2,000F/cm³, about 1,250 F/cm³ to about 1,500 F/cm³, about 1,250 F/cm³ toabout 1,625 F/cm³, about 1,250 F/cm³ to about 1,750 F/cm³, about 1,250F/cm³ to about 2,000 F/cm³, about 1,500 F/cm³ to about 1,625 F/cm³,about 1,500 F/cm³ to about 1,750 F/cm³, about 1,500 F/cm³ to about 2,000F/cm³, about 1,625 F/cm³ to about 1,750 F/cm³, about 1,625 F/cm³ toabout 2,000 F/cm³, or about 1,750 F/cm³ to about 2,000 F/cm³.

In some embodiments, the supercapacitor is capable of outputting avoltage of about 50 V to about 250 V. In some embodiments, thesupercapacitor is capable of outputting a voltage of at least about 50V. In some embodiments, the supercapacitor is capable of outputting avoltage of about 50 V to about 75 V, about 50 V to about 100 V, about 50V to about 125 V, about 50 V to about 150 V, about 50 V to about 175 V,about 50 V to about 200 V, about 50 V to about 225 V, about 50 V toabout 250 V, about 75 V to about 100 V, about 75 V to about 125 V, about75 V to about 150 V, about 75 V to about 175 V, about 75 V to about 200V, about 75 V to about 225 V, about 75 V to about 250 V, about 100 V toabout 125 V, about 100 V to about 150 V, about 100 V to about 175 V,about 100 V to about 200 V, about 100 V to about 225 V, about 100 V toabout 250 V, about 125 V to about 150 V, about 125 V to about 175 V,about 125 V to about 200 V, about 125 V to about 225 V, about 125 V toabout 250 V, about 150 V to about 175 V, about 150 V to about 200 V,about 150 V to about 225 V, about 150 V to about 250 V, about 175 V toabout 200 V, about 175 V to about 225 V, about 175 V to about 250 V,about 200 V to about 225 V, about 200 V to about 250 V, or about 225 Vto about 250 V.

Other goals and advantages of the invention will be further appreciatedand understood when considered in conjunction with the followingdescription and accompanying drawings. While the following descriptionmay contain specific details describing particular embodiments of theinvention, this should not be construed as limitations to the scope ofthe invention but rather as an exemplification of preferableembodiments. For each aspect of the invention, many variations arepossible as suggested herein that are known to those of ordinary skillin the art. A variety of changes and modifications can be made withinthe scope of the invention without departing from the spirit thereof.

BRIEF DESCRIPTION OF DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings or figures (also “FIG.” and “FIGs.” herein), ofwhich:

FIG. 1A shows an example of an electrode comprising a compact thick filmof metal oxide, in accordance with some embodiments.

FIG. 1B shows an example of an electrode comprising a nanostructuredmetal oxide films, in accordance with some embodiments.

FIG. 1C shows an example of an electrode with conductive materials addedto the nanostructured metal oxide, in accordance with some embodiments.

FIG. 1D shows an example of an electrode comprising nanostructured metaloxide grown on 3D interconnected corrugated carbon-based networks(ICCNs) with high surface area and high electronic conductivity, inaccordance with some embodiments.

FIG. 2A is an exemplary schematic diagram of a fabrication procedure forlaser-scribed graphene (LSG)-MnO₂ electrodes, in accordance with someembodiments.

FIG. 2B provides exemplary digital photographs showing a GO film beforeand after laser scribing, in accordance with some embodiments.

FIG. 2C shows an exemplary graph of mass loading of MnO₂ versusdeposition time, in accordance with some embodiments.

FIG. 2D shows exemplary variation of resistance of an LSG-MnO₂ electrodeas a function of bending radius, in accordance with some embodiments.

FIG. 2E shows exemplary changes in resistance of an LSG-MnO₂ electrodeunder repeated bending cycles for a concave bend radius of 5 mm, and anexemplary inset photograph showing flexibility of an LSG-MnO₂ electrode,in accordance with some embodiments.

FIG. 3A shows an exemplary scanning electron microscopy (SEM) image ofan LSG-MnO₂ electrode at low magnification, in accordance with someembodiments.

FIG. 3B shows an exemplary SEM image of an LSG-MnO₂ electrode at highmagnification, in accordance with some embodiments.

FIG. 3C provides an exemplary SEM image that shows nanoflower morphologyof electrodeposited MnO₂, in accordance with some embodiments.

FIG. 3D shows an exemplary cross-sectional SEM image of LSG-MnO₂, inaccordance with some embodiments.

FIG. 3E shows an exemplary energy-dispersive X-ray spectroscopy (EDS)elemental mapping of C (red), Mn (blue), and O (green), in accordancewith some embodiments.

FIG. 3F shows exemplary X-ray photoelectron spectroscopy (XPS) spectraof Mn 2p showing a doublet with a peak-to-peak separation of 11.6 eV, inaccordance with some embodiments.

FIG. 3G shows exemplary XPS spectra of Mn 3s, in accordance with someembodiments.

FIG. 4A shows an exemplary schematic of an LSG-MnO₂ symmetricsupercapacitor device, in accordance with some embodiments.

FIG. 4B shows exemplary cyclic voltammetry (CV) profiles for an LSG-MnO₂(3 min) supercapacitor at different scan rates, in accordance with someembodiments.

FIG. 4C shows exemplary evolution of stack capacitance of LSG withvarious mass loadings of MnO₂ as a function of scan rate, in accordancewith some embodiments.

FIG. 4D shows exemplary specific capacitance due to MnO₂ only as afunction of the loadings measured at a scan rate of 1 mV/s, inaccordance with some embodiments.

FIG. 4E shows exemplary charge-discharge curves of an LSG-MnO₂ (3 min)supercapacitor at different current densities, in accordance with someembodiments.

FIG. 4F shows exemplary change of stack capacitance of an LSG-MnO₂ (120min) supercapacitor as a function of current density and data forCCG-MnO₂ (120 min) and Au—MnO₂ (120 min) supercapacitors are presentedfor comparison, in accordance with some embodiments.

FIG. 4G shows exemplary progression of real (C′) and imaginary (C″)parts of stack capacitance of CCG as a function of frequency, inaccordance with some embodiments.

FIG. 4H shows exemplary progression of real (C′) and imaginary (C″)parts of stack capacitance of LSG as a function of frequency, inaccordance with some embodiments.

FIG. 4I provides an exemplary comparison of an LSG-MnO₂ (120 min) hybridcapacitor with examples of an activated carbon supercapacitor (2.7 V/10F), a pseudocapacitor (2.6 V/35 mF), and a lithium-ion hybrid capacitor(2.3 V/220 F), in accordance with some embodiments.

FIG. 5A is an exemplary schematic showing an example structure of anassembled supercapacitor device based on graphene-MnO₂ as positiveelectrode and LSG as negative electrode in 1.0 M Na₂SO₄ electrolyte, inaccordance with some embodiments.

FIG. 5B shows exemplary CV curves of an asymmetric supercapacitor afterincreasing the potential window from 0.8 to 2.0 V, in accordance withsome embodiments.

FIG. 5C shows exemplary charge discharge curves of an asymmetricsupercapacitor after increasing the potential window from 0.8 to 2.0 V,in accordance with some embodiments.

FIG. 5D shows exemplary change of the stack capacitance as a function ofcurrent density, in accordance with some embodiments.

FIG. 5E shows exemplary electrochemical performance of the device underdifferent bending angles, in accordance with some embodiments.

FIG. 5F shows exemplary cycling stability of the device tested over10,000 cycles at a scan rate of 1,000 mV/s, and change of equivalentseries resistance (ESR) during cycling, in accordance with someembodiments.

FIGS. 6A-C illustratively show an exemplary fabrication process for anasymmetric microsupercapacitor device based on LSG-MnO₂ as positiveelectrode and LSG as negative electrode, in accordance with someembodiments.

FIG. 6D is an exemplary photograph showing the asymmetricmicrosupercapacitor, in accordance with some embodiments.

FIG. 6E is an exemplary optical microscope image showing theLSG-GO/LSG-MnO₂ interface, in accordance with some embodiments.

FIG. 6F is an exemplary SEM image of an interface between GO and LSGshowing selective electrodeposition of MnO₂ on LSG only and the insetprovides a magnified view of the GO and LSG area, in accordance withsome embodiments.

FIG. 6G provides an exemplary comparison of stack capacitance of thesupercapacitor between the sandwich structure and the planarinterdigitated structure for an asymmetric, MnO₂ deposition time 3 mindevice, in accordance with some embodiments.

FIG. 6H provides the exemplary stack and areal capacitance of LSG-MnO₂supercapacitors with deposition times of 0 to 120 minutes.

FIG. 6I provides the exemplary stack and areal capacitance of LSG-MnO₂supercapacitors with deposition times of 576 and 960 minutes.

FIG. 7 shows an exemplary Ragone plot comparing energy and power densityof LSG-MnO₂ supercapacitors with energy storage devices including a leadacid battery, a lithium thin-film battery, an aluminum electrolyticcapacitor, activated carbon supercapacitors of variable sizes, apseudocapacitor, and a lithium-ion hybrid capacitor, in accordance withsome embodiments. Performance data for Au—MnO₂ and CCG-MnO₂ are alsoincluded which reveal the importance of the microstructure of theelectrodes, in accordance with some embodiments.

FIG. 8A schematically illustrates exemplary direct fabrication of anasymmetric supercapacitor array consisting of 9 cells in a single step

FIG. 8B shows charge-discharge curves of asymmetric supercapacitorarrays connected in series (3 cells in series, 3S), in parallel (3 cellsin parallel, 3P), and in a combination of series and parallel (3series×3 parallel, 3S×3P), in accordance with some embodiments, and asingle device (1 cell) for comparison, in accordance with someembodiments.

FIG. 8C schematically illustrates an exemplary integration of asupercapacitor array with solar cells for efficient solar energyharvesting and storage, in accordance with some embodiments.

FIG. 8D schematically illustrates an exemplary integration of asupercapacitor array with solar cells in sun and at night, in accordancewith some embodiments.

FIG. 9A schematically illustrates an exemplary converted graphene (CCG)film, and in accordance with some embodiments.

FIG. 9B illustrates the exemplary effect of the pore structure of a CCGon its electrochemical performance, in accordance with some embodiments.

FIG. 9C schematically illustrates an exemplary laser-scribed graphene(LSG) film, in accordance with some embodiments.

FIG. 9D illustrates the exemplary effect of the pore structure of a LSGon its electrochemical performance, in accordance with some embodiments.

FIG. 10 shows exemplary Nyquist impedance plots of CCG/MnO₂ andLSG-MnO₂, in accordance with some embodiments.

FIG. 11 shows exemplary evolution of a surface of LSG-MnO₂, inaccordance with some embodiments.

FIG. 12 is an example of a light scribed writing LSG microsupercapacitorarray, in accordance with some embodiments.

FIG. 13 schematically illustrates exemplary fabrication of an array of 9asymmetric cells connected in series/parallel, in accordance with someembodiments.

FIG. 14A shows an exemplary finished array of 9 asymmetric cellsconnected 3 in series×3 in parallel, in accordance with someembodiments.

FIG. 14B shows an exemplary circuit illustration of the fullmicrosupercapacitor array in accordance with some embodiments.

FIG. 15 schematically illustrates exemplary fabrication of an array of 9symmetric supercapacitors connected in series and/or parallel, inaccordance with some embodiments.

FIG. 16 shows examples of supercapacitor arrays that are connected inseries, parallel and in combinations of the two, in accordance with someembodiments.

FIG. 17 shows examples of electrochemical performance of asymmetricsupercapacitor arrays, in accordance with some embodiments.

FIG. 18A shows an exemplary image of a LSG microsupercapacitor arraywherein graphene is used to connect the supercapacitor cells, inaccordance with some embodiments.

FIG. 18B shows an exemplary image of a flexed LSG microsupercapacitorarray wherein graphene is used to connect the supercapacitor cells, inaccordance with some embodiments.

DETAILED DESCRIPTION

Provided herein are devices comprising one or more cells, and methodsfor fabrication thereof. The devices may be electrochemical devices. Thedevices may include three-dimensional supercapacitors. The devices maybe microdevices such as, for example, microsupercapacitors. In someembodiments, the devices are three-dimensional hybridmicrosupercapacitors. The devices may be configured for high voltageapplications (e.g., microdevices for high voltage applications). In someembodiments, the devices are high voltage microsupercapacitors. Incertain embodiments, the devices are high voltage asymmetricmicrosupercapacitors. In some embodiments, the devices are integratedmicrosupercapacitors for high voltage applications.

The present disclosure provides systems and methods for directpreparation of devices (e.g., high-voltage devices) such as, forexample, high-voltage supercapacitors. The high-voltage supercapacitorsmay include microsupersupercapacitors. The high-voltage devices may beprepared in a single step. The high-voltage devices may be preparedusing one package. The high-voltage devices may be prepared in a singlestep and using one package. One package may advantageously be usedinstead of a plurality (e.g., instead of hundreds in the traditionalmodules).

A high-voltage device (e.g., a high-voltage supercapacitor) may have avoltage of greater than or equal to about 5 volts (V), 10 V, 15 V, 20 V,30 V, 40 V, 50 V, 60 V, 70 V, 80 V, 90 V, 100 V, 110 V, 120 V, 130 V,140 V, 150 V, 160 V, 170 V, 180 V, 190 V, 200 V, 210 V, 220 V, 230 V,240 V, 250 V, 260 V, 270 V, 280 V, 290 V, 300 V, 310 V, 320 V, 330 V,340 V, 350 V, 360 V, 370 V, 380 V, 390 V, 400 V, 410 V, 420 V, 430 V,440 V, 450 V, 460 V, 470 V, 480 V, 490 V, 500 V, 510 V, 520 V, 530 V,540 V, 550 V, 560 V, 570 V, 580 V, 590 V, 600 V, 650 V, 700 V, 750 V,800 V, 850 V, 900 V, 950 V, 1,000 V, 1,050 V, 1,100 V, 1,150 V, 1,200 V,1,250 V, 1,300 V, 1,350 V, 1,400 V, 1,450 V, or 1,500 V.

A high-voltage device (e.g., high-voltage supercapacitor) may have avoltage of less than about 10 V, 15 V, 20 V, 30 V, 40 V, 50 V, 60 V, 70V, 80 V, 90 V, 100 V, 110 V, 120 V, 130 V, 140 V, 150 V, 160 V, 170 V,180 V, 190 V, 200 V, 210 V, 220 V, 230 V, 240 V, 250 V, 260 V, 270 V,280 V, 290 V, 300 V, 310 V, 320 V, 330 V, 340 V, 350 V, 360 V, 370 V,380 V, 390 V, 400 V, 410 V, 420 V, 430 V, 440 V, 450 V, 460 V, 470 V,480 V, 490 V, 500 V, 510 V, 520 V, 530 V, 540 V, 550 V, 560 V, 570 V,580 V, 590 V, 600 V, 650 V, 700 V, 750 V, 800 V, 850 V, 900 V, 950 V,1,000 V, 1,050 V, 1,100 V, 1,150 V, 1,200 V, 1,250 V, 1,300 V, 1,350 V,1,400 V, 1,450 V, or 1,500 V.

In some embodiments, a high-voltage or supercapacitor may have a voltageof at least about 100 V. In some embodiments, a high-voltage device orsupercapacitor may have a voltage of at least about 180 V. In someembodiments, a high-voltage device or supercapacitor may have a voltageof less than or equal to about 600 V, 550 V, or 500 V. In someembodiments, a high-voltage device or supercapacitor may have a voltageof from about 100 V to 540 V, from 180 V to 540 V, from 100 V to 200 V,from 100 V to 300 V, from 180 V to 300 V, from 100 V to 400 V, from 180V to 400 V, from 100 V to 500 V, from 180 V to 500 V, from 100 V to 600V, from 180 V to 600 V, from 100 V to 700 V, from 180 V to 700 V, from150 V to 1,000 V, or from 150 V to 1,100 V.

High-voltage devices of the disclosure may comprise interconnectedcells. In some embodiments, the cells can be electrochemical cells. Insome embodiments, the cells can be individual supercapacitor cells. Thecells may be interconnected to achieve a high voltage and/or for otherpurposes. Any aspects of the disclosure described in relation to amicrosupercapacitor may equally apply to a supercapacitor at least insome configurations, and vice versa. In some embodiments, thesupercapacitor cells may be microsupercapacitor cells. A cell maycomprise symmetric or asymmetric electrodes.

A plurality of cells may be interconnected to form supercapacitorsand/or other devices. In some embodiments, the devices can be batteriesand/or various types of capacitors. In some embodiments, at least about2, 5, 10, 20, 30, 40, 50, 75, 100, 125, 150, 200, 250, 300, 350, 400,500, 600, 700, 800, 900, 1000, 1500, 2000, or more cells may beinterconnected. In some embodiments, between about 50 and 300 cells maybe interconnected. In some embodiment, the cells are connected inseries. In some embodiments, the cells are connected in parallel. Insome embodiments, the cells are connected in series and in parallel.

A supercapacitor may operate using one or more charge storagemechanisms. In some embodiments, the supercapacitor may operate usingpseudocapacitor charge storage mechanisms. In some embodiments, thesupercapacitor may operate using electric double-layer capacitor (EDLC)charge storage mechanisms. In some embodiments, the supercapacitor mayoperate using a combination of pseudocapacitor and electric double-layercapacitor (EDLC) charge storage mechanisms. In some embodiments, chargemay be stored with the aid of both Faradaic and non-Faradaic processes.Such a supercapacitor may be referred to as a hybrid supercapacitor. Insome embodiments, hybrid charge storage mechanism(s) occur at a singleelectrode. In some embodiments, hybrid charge storage mechanism(s) occurat a both electrodes. Hybrid supercapacitors may comprise symmetric orasymmetric electrodes.

A cell may comprise an electrolyte. In some embodiments, the cell is asupercapacitor cell. Electrolytes may include aqueous electrolytes,organic electrolytes, ionic liquid-based electrolytes, or anycombination thereof. In some embodiments, the electrolyte may be liquid,solid, and/or a gel. In some embodiments, an ionic liquid may behybridized with another solid component to form a gel-like electrolyte(also “ionogel” herein). The solid component may be a polymer. The solidcomponent may be silica. In some embodiments, the solid component can befumed silica. An aqueous electrolyte may be hybridized with a polymer toform a gel-like electrolyte (also “hydrogel” and “hydrogel-polymer”herein). An organic electrolyte may be hybridized with a polymer to forma gel-like electrolyte.

Electrolytes may comprise aqueous potassium hydroxide; hydrogelcomprising poly(vinyl alcohol) (PVA)-H₂SO₄ or PVA-H₃PO₄; aqueouselectrolyte of phosphoric acid (H₃PO₄); tetraethyl ammoniumtetrafluoroborate (TEABF₄) dissolved in acetonitrile,1-ethyl-3-methylimidazoliumtetrafluoroborate (EMIMBF₄; ionogelcomprising fumed silica (e.g., fumed silica nano-powder) mixed with anionic liquid (e.g., 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide (BMIMNTf₂)); and the like. Suchelectrolytes may provide a range of voltage windows, including at leastabout 0.5 V, 1 V, 2 V, 3 V, 4 V, or more. In some embodiments, theionogel comprising fumed silica nano-powder with the ionic liquidBMIMNTf₂ may provide a voltage window of about 2.5 V. In someembodiments, hydrogel-polymer electrolytes may provide a voltage windowof about 1 V. In some embodiments, a cell comprises an aqueouselectrolyte.

The active material in the electrodes may comprise carbonaceousmaterials, one or more metal oxides, and/or other suitable materials. Insome embodiments, the active material in the electrodes can be carbon.In some embodiments, the carbon can comprise activated carbon, graphene,interconnected corrugated carbon-based network (ICCN), or anycombination thereof. The active material in the electrodes may comprisea highly conductive and high surface area laser-scribed graphene (LSG)framework that is a form of interconnected corrugated carbon-basednetwork (ICCN). The ICCN may be produced from light scribing (e.g.,laser scribing) of carbon-based films such as graphite oxide (GO). Anyaspects of the disclosure described in relation to graphene (in thecontext of light scribed or three-dimensional materials) or LSG mayequally apply to ICCN at least in some configurations, and vice versa.

An ICCN may comprise a plurality of expanded and interconnected carbonlayers. For the purpose of this disclosure, in certain embodiments, theterm “expanded,” referring to a plurality of carbon layers that areexpanded apart from one another, means that a portion of adjacent onesof the carbon layers are separated by at least about 2 nanometers (nm).In some embodiments, at least a portion of adjacent carbon layers areseparated by greater than or equal to about 2 nm, 3 nm, 4 nm, 5 nm, 6nm, 7 nm, 8 nm, 9 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm,45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95nm, or 100 nm. In some embodiments, at least a portion of adjacentcarbon layers are separated by less than about 3 nm, 4 nm, 5 nm, 6 nm, 7nm, 8 nm 9 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm,50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, or100 nm. In some embodiments, at least a portion of adjacent carbonlayers are separated by between about 2 nm and 10 nm, 2 nm and 25 nm, 2nm and 50 nm, or 2 nm and 100 nm. In some embodiments, each of theplurality of carbon layers is a two-dimensional material with only onecarbon atom of thickness. In some embodiments, each of the expanded andinterconnected carbon layers may comprise at least one, or a pluralityof corrugated carbon sheets that are each one atom thick. In anotherembodiment, each of the expanded and interconnected carbon layerscomprises a plurality of corrugated carbon sheets. The thickness of theICCN, as measured from cross-sectional scanning electron microscopy(SEM) and profilometry, can be found to be around about 7.6 micrometerin one embodiment. In another embodiment, a range of thicknesses of theplurality of expanded and interconnected carbon layers making up theICCN is from about 7 micrometer to 8 micrometer.

An ICCN may have a combination of properties that include, for example,high surface area and high electrical conductivity in an expandedinterconnected network of carbon layers. In some embodiments, theplurality of expanded and interconnected carbon layers has a surfacearea of greater than or equal to about 500 square meters per gram(m²/g), 1000 m²/g, 1400 m²/g, 1500 m²/g, 1520 m²/g, 1750 m²/g or 2000m²/g. In some embodiments, the plurality of expanded and interconnectedcarbon layers has a surface area of between about 100 m²/g and 1500m²/g, 500 m²/g and 2000 m²/g, 1000 m²/g and 2500 m²/g, or 1500 m²/g and2000 m²/g. The plurality of expanded and interconnected carbon layersmay have such surface areas in combination with one or more electricalconductivities (e.g., one or more electrical conductivities providedherein).

In some embodiments, the electrical conductivity of the plurality ofexpanded and interconnected carbon layers is at least about 0.1 S/m, orat least about 0.5 S/m, or at least about 1 S/m, or at least about 5S/m, or at least about 10 S/m, or at least about 15 S/m, or at leastabout 25 S/m, or at least about 50 S/m, or at least about 100 S/m, or atleast about 200 S/m, or at least about 300 S/m, or at least about 400S/m, or at least about 500 S/m, or at least about 600 S/m, or at leastabout 700 S/m, or at least about 800 S/m, or at least about 900 S/m, orat least about 1,000 S/m, or at least about 1,100 S/m, or at least about1,200 S/m, or at least about 1,300 S/m, or at least about 1,400 S/m, orat least about 1,500 S/m, or at least about 1,600 S/m, or at least about1,700 S/m. In one embodiment, the plurality of expanded andinterconnected carbon layers yields an electrical conductivity that isat least about 1700 S/m and a surface area that is at least about 1500m²/g. In another embodiment, the plurality of expanded andinterconnected carbon layers yields an electrical conductivity of about1650 S/m and a surface area of about 1520 m²/g.

An ICCN may possess a very low oxygen content of only about 3.5%, whichcontributes to a relatively very high charging rate. In otherembodiments, the oxygen content of the expanded and interconnectedcarbon layers ranges from about 1% to about 5%.

The active material in the electrodes may comprise a porous ICCNcomposite that includes metallic nanoparticles disposed within theplurality of pores of the ICCN. In some embodiments, the active materialcomprises graphene LSG/metal oxide nanocomposite). In some embodiments,the metallic nanoparticles may be disposed within the plurality of poresthrough electrodeposition or any other suitable technique. The metallicnanoparticles may have shapes that include, but are not limited to,nanoflower shapes, flake shapes, and combinations thereof. The metallicnanoparticles may comprise one or more metals, metal oxides, metalhydroxides, or any combination thereof. In some embodiments, themetallic nanoparticles may be metal particles, metal oxide particles, orany combination thereof. In some embodiments, the metallic nanoparticlesmay comprise an oxide or hydroxide of manganese, ruthenium, cobalt,nickel, iron, copper, molybdenum, vanadium, nickel, or a combination ofone or more thereof. In some embodiments, the metallic nanoparticles maycomprise (e.g., comprise (or be) particles of) platinum (Pt), palladium(Pd), silver (Ag), gold (Au), or any combination thereof. In someembodiments, the metallic nanoparticles may be metal particles thatinclude, but are not limited to, Pt, Pd, Ag, Au, and combinationsthereof. In some embodiments, the metallic nanoparticles comprise MnO₂,RuO₂, Co₃O₄, NiO, Fe₂O₃, CuO, MoO₃, V₂O₅, Ni(OH)₂, or any combinationthereof.

In some embodiments, a porous ICCN composite may be produced byproviding a film comprising a mixture of a metallic precursor and acarbon-based oxide and exposing at least a portion of the film to lightto form a porous interconnected corrugated carbon-based network (ICCN)composite. The porous ICCN composite may comprise a plurality of carbonlayers that are interconnected and expanded apart from one another toform a plurality of pores, and metallic nanoparticles disposed withinthe plurality of pores. The light may convert the metallic precursor tothe metallic nanoparticles. Providing the film made of the mixture ofthe metallic precursor and the carbon-based oxide may comprise providinga solution comprising a liquid, the metallic precursor, and thecarbon-based oxide; disposing the solution with the liquid, the metallicprecursor, and the carbon-based oxide onto a substrate; and evaporatingthe liquid from the solution to form the film. The carbon-based oxidemay be graphite oxide. The metallic nanoparticles may be, for example,particles of RuO₂, Co₃O₄, NiO, V₂O₅, Fe₂O₃, CuO, MoO₃, or anycombination thereof.

In some embodiments, a porous ICCN composite may be produced wherein apercentage of surface area coverage of the metallic nanoparticles ontothe plurality of carbon layers ranges from about 10% to about 95%. Insome embodiments, the percentage of surface area coverage of themetallic nanoparticles onto the plurality of carbon layers is at leastabout 15%, at least about 20%, at least about 25%, at least about 30%,at least about 35%, at least about 40%, at least about 45%, at leastabout 50%, at least about 60%, at least about 70%, at least about 80%,at least about 90%, or at least about 95%.

In some embodiments, a porous ICCN composite may be produced wherein theporous ICCN composite provides an energy density that ranges from about2 Watt-hour/liter to about 41 Watt-hour/liter. In certain embodiments,the porous ICCN composite provides an energy density that is at leastabout 2 Watt-hour/liter, at least about 5 Watt-hour/liter, at leastabout 10 Watt-hour/liter, at least about 15 Watt-hour/liter, at leastabout 20 Watt-hour/liter, at least about 25 Watt-hour/liter, at leastabout 30 Watt-hour/liter, at least about 35 Watt-hour/liter, or at leastabout 40 Watt-hour/liter.

Methods of producing porous ICCN composite are provided herein. Forexample, in one embodiment, the method comprises: providing a filmcomprising a mixture of a metallic precursor and a carbon-based oxide;and exposing at least a portion of the film to light to form a porousinterconnected corrugated carbon-based network (ICCN) compositecomprising: a plurality of carbon layers that are interconnected andexpanded apart from one another to form a plurality of pores; andmetallic nanoparticles disposed within the plurality of pores, whereinthe light converts the metallic precursor to the metallic nanoparticles.In further or additional embodiments, a method of producing porous ICCNcomposite is provided wherein providing the film made of the mixture ofthe metallic precursor and the carbon-based oxide comprises: providing asolution comprising a liquid, the metallic precursor, and thecarbon-based oxide; disposing the solution with the liquid, the metallicprecursor, and the carbon-based oxide onto a substrate; and evaporatingthe liquid from the solution to form the film. In one embodiment, amethod of producing porous interconnected corrugated carbon-basednetwork (ICCN) composite is provided comprising: forming a porous ICCNcomprising a plurality of carbon layers that are interconnected andexpanded apart from one another to form a plurality of pores; andelectrodepositing metallic nanoparticles within the plurality of pores.In another embodiment, the method comprises providing a film made of themixture of the metallic precursor and the carbon-based oxide thatcomprises: providing a solution comprising a liquid, the metallicprecursor, and the carbon-based oxide; disposing the solution with theliquid, the metallic precursor, and the carbon-based oxide onto asubstrate; and evaporating the liquid from the solution to form thefilm. In certain applications, the carbon-based oxide is graphite oxide.The metallic nanoparticles may be particles of MnO₂, RuO₂, Co₃O₄, NiO,V₂O₅, Fe₂O₃, CuO, MoO₃, Ni(OH)₂, or any combination thereof.

In another aspect, methods for electrodepositing the metallicnanoparticles within the plurality of pores comprise: submerging theporous ICCN into an aqueous solution having a metal precursor; andapplying an electrical current through the porous ICCN to electrodepositthe metallic nanoparticles into the plurality of pores. In someembodiments, the electrical current has a current density of at leastabout 250 mA/cm². In some embodiments, the electrical current has acurrent density of at least about 350 mA/cm², at least about 450 mA/cm²,at least about 550 mA/cm², at least at least about 650 mA/cm², at leastabout 750 mA/cm², or at least about 1,000 mA/cm².

The porous ICCN or ICCN composite may be formed by exposing thecarbon-based oxide to light from a light source. The light source maycomprise a laser, a flash lamp, or other equally high intensity sourcesof light capable of reducing the carbon-based oxide to the porous ICCN.Any aspects of the disclosure described in relation to laser-scribedmaterials may equally apply to light-scribed materials at least in someconfigurations, and vice versa.

Devices herein, including supercapacitors and/or microsupercapacitors,may be configured in different structures. In some embodiments, thedevices may be configured in stacked structures, planar structures,spirally wound structures, or any combination thereof. In someembodiments, the devices may be configured to comprising stackedelectrodes. In some embodiments, the devices may be configured tocomprise interdigitated electrodes. In some embodiments, the devices maybe configured in a sandwich structure or an interdigitated structure.

Supercapacitors

Supercapacitors may be classified according to their charge storagemechanism as either electric double-layer capacitors (EDLCs) orpseudocapacitors. In EDLCs, charge can be stored through rapidadsorption-desorption of electrolyte ions on high-surface-area carbonmaterials. Pseudocapacitors can store charge via fast and reversibleFaradaic reactions near the surface of metal oxides or conductingpolymers. In some embodiments, the supercapacitors comprise symmetricEDLCs with activated carbon electrodes and organic electrolytes that canprovide cell voltages as high as 2.7 V. Although these EDLCs can exhibithigh power density and excellent cycle life, they can suffer from lowenergy density because of the limited capacitance of carbon-basedelectrodes. Faradaic electrodes can have a specific pseudocapacitance(e.g., 300-1,000 F/g) that exceeds that of carbon-based EDLCs; however,their performance can degrade quickly upon cycling.

Hybrid systems may be used as an alternative to EDLCs andpseudocapacitors. Using both Faradaic and non-Faradaic processes tostore charge, hybrid capacitors can achieve energy and power densitiesgreater than EDLCs without sacrificing cycling stability andaffordability that limits pseudocapacitors. Hybrid supercapacitors maycomprise RuO₂, Co₃O₄, NiO, V₂O₅, Ni(OH)₂, MnO₂, or any combinationthereof. MnO₂-based systems may be attractive, as MnO₂ is anearth-abundant and environmentally friendly material with a theoreticalspecific capacitance (e.g., a high theoretical specific capacitance) of1,380 farads per gram (F/g); however, poor ionic (10⁻¹³ S/cm) andelectronic (10⁻⁵-10⁻⁶ S/cm) conductivity of pristine MnO₂ can limit itselectrochemical performance.

In some embodiments, ultrathin MnO₂ films that are a few tens ofnanometers in thickness may be used. However, thickness andarea-normalized capacitance of these electrodes may not be adequate formost applications.

In some embodiments, nanostructured manganese dioxide (MnO₂) may beincorporated on highly conductive support materials with high surfaceareas such as nickel nanocones, Mn nanotubes, activated carbon, carbonfabric, conducting polymers, carbon nanotubes or graphene. Specificcapacitances of 148-410 F/g may be achieved under slow charge-dischargerates but may decrease rapidly as the discharge rate is increased.Further, these materials may have low packing density with large porevolume, meaning that a huge amount of electrolyte is needed to build thedevice, which adds to the mass of the device without adding anycapacitance. The energy density and power density on the device levelmay be very limited.

In some embodiments, hybrid electrodes based on 3D ICCN doped with MnO₂nanoflowers may be used. The structure of the ICCN substrate may beconfigured (e.g., rationally designed) to achieve high conductivity,suitable porosity, and/or high specific surface area. Such propertiesmay result in not only a high gravimetric capacitance, but also improvedvolumetric capacitance. Furthermore, the high surface area ofnanostructured MnO₂ can provide more active sites for Faradaic reactionsand shorten ion diffusion pathways that are crucial for realizing itsfull pseudocapacitance. Hybrid supercapacitors based on these materialscan achieve energy densities of, for example, up to about 42 Wh/Lcompared with about 7 Wh/L for state-of-the-art commercially availablecarbon-based supercapacitors. These ICCN-MnO₂ hybrid supercapacitors mayuse aqueous electrolytes and may be assembled in air without the needfor the expensive dry rooms required for building today'ssupercapacitors.

Reference will now be made to the figures. It will be appreciated thatthe figures and features therein are not necessarily drawn to scale.

Three-Dimensional (3D) Hybrid Supercapacitors and Microsupercapacitors

The present disclosure provides methods for engineeringthree-dimensional (3D) hybrid supercapacitors and microsupercapacitors.Such devices may be configured (e.g., engineered) for high-performanceenergy storage. In some embodiments, such devices are configured (e.g.,engineered) for high-performance integrated energy storage. The 3Dhigh-performance hybrid supercapacitors and microsupercapacitors may bebased, for example, on ICCN and MnO₂. The 3D high-performance hybridsupercapacitors and microsupercapacitors may be configured by rationallydesigning the electrode microstructure and combining active materialswith electrolytes that operate at high voltages. In some examples, thisresults in hybrid electrodes with a volumetric capacitance (e.g., anultrahigh volumetric capacitance) of at least about 1,100 F/cm³,corresponding to a specific capacitance of the constituent MnO₂ of about1,145 F/g, which is close to the theoretical value of 1,380 F/g. Energydensity of the full device can vary, for example, between about 22 Wh/Land 42 Wh/L depending on the device configuration. In certainembodiments, such energy densities can be superior to (e.g., higherthan) those of commercially available double-layer supercapacitors,pseudocapacitors, lithium-ion capacitors, and/or hybrid supercapacitors(e.g., commercially available hybrid supercapacitors comprising NiOOHpositive electrode and activated carbon negative electrode, or PbO₂positive electrode and activated carbon negative electrode) tested underthe same conditions and/or comparable to that of lead acid batteries.These hybrid supercapacitors may use aqueous electrolytes and may beassembled in air without the need for expensive dry rooms required forbuilding today's supercapacitors.

In some examples, specific capacitance of the constituent metal or metaloxide (e.g., MnO₂) may be at least about 50%, 60%, 70%, 75%, 80%, 81%,82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%,96%, 97%, 98%, or 99% of the theoretical capacitance of the constituentmetal or metal oxide (e.g., MnO₂). The electrode(s) may have suchspecific capacitance at a given mass loading of the constituent metal ormetal oxide (e.g., MnO₂).

The electrode(s) may have a mass loading of the constituent metal ormetal oxide (e.g., MnO₂) of at least about 5%, 10%, 13%, 15%, 20%, 25%,30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or99%. The electrode(s) may have a mass loading of the constituent metalor metal oxide (e.g., MnO₂) of less than or equal to about 5%, 10%, 13%,15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%,85%, 90%, 95%, or 99%. The electrode(s) may have a mass loading of theconstituent metal or metal oxide (e.g., MnO₂) of about 10% to about 20%,from about 10% to about 50%, from about 10% to about 75%, or from about10% to about 90%.

In some examples, a supercapacitor and/or microsupercapacitor herein canhave a capacitance per footprint (also “areal capacitance” herein) ofgreater than or equal to about 0.3 F/cm², 0.4 F/cm², 0.5 F/cm², 0.6F/cm², 0.7 F/cm², or 0.8 F/cm² (e.g., see TABLES 1-2). In some examples,a supercapacitor and/or microsupercapacitor herein can have acapacitance per footprint between about 0.3 F/cm² and 0.8 F/cm², 0.4F/cm² and 0.8 F/cm², 0.5 F/cm² and 0.8 F/cm², 0.6 F/cm² and 0.8 F/cm²,or 0.7 F/cm² and 0.8 F/cm². In some examples, a supercapacitor and/ormicrosupercapacitor herein can have a capacitance per footprint at leastabout 2, 3, 4, 5, 6, 7, 8, 9, or 10 times greater than a commercialcarbon supercapacitor. In some examples, a hybrid electrode herein canhave a volumetric capacitance of greater than or equal to about 50F/cm³, 100 F/cm³, 150 F/cm³, 200 F/cm³, 400 F/cm³, 600 F/cm³, 800 F/cm³,1,000 F/cm³, 1,100 F/cm³, 1,200 F/cm³, 1,300 F/cm³, 1,400 F/cm³, or1,500 F/cm³ (e.g., when calculated based on the volume of the activematerial per electrode only).

In designing supercapacitor electrodes, special efforts can be made toensure that they are capable of providing high energy density and highpower density. This may require optimization of the preparationconditions to facilitate ionic and electronic transport within theelectrodes as illustrated in FIGS. 1A-D. Rationally designinghigh-performance hybrid supercapacitors can include rationally designinghigh-energy-high-power hybrid supercapacitor electrodes.

FIGS. 1A-D schematically illustrate rational design ofhigh-energy-high-power hybrid supercapacitor electrodes. The method caninclude improving ionic current (IC) and electronic current (EC) withinthe electrode (e.g., improving the IC and the EC can be key). To achievehigh-energy and high-power supercapacitors, both the ionic andelectronic currents within the electrodes may need to be facilitated.This can be very challenging (e.g., with metal oxide pseudocapacitors)because of low electrical conductivity and long ionic diffusion pathwaysof some metal oxide films.

As illustrated in FIG. 1A, in a compact MnO₂ thick film electrode 101,only the top layer may be exposed to the electrolyte such that a limitedamount of the active material is involved in charge storage.

Electrochemical utilization of electrodes can be improved by usingnanostructured MnO₂ such as nanoparticles, nanorods, nanowires, andnanoflowers. As shown in FIG. 1B, the porous structure of a porouselectrode 102 can increase or maximize the area of active material thatis exposed to the electrolyte and thus available to discharge comparedto a solid electrode surface. Although this system can exhibit higherenergy density than the system in FIG. 1A, it can still suffer from theinherently low electrical conductivity of MnO₂ leading to low poweroutput.

To improve the electrical conductivity of MnO₂ film, conductivematerials such as carbon powder, carbon nanotubes, and graphene can beintroduced into nanostructured MnO₂ electrodes 103. In such instances,the electronic charge carriers may need to move through smallinter-particle contact areas which exhibit additional resistance,resulting in poor electron transport from the electrode material to thecurrent collector, as shown in FIG. 1C.

FIG. 1D shows an electrode obtained by growing MnO₂ nanostructures ontoa 3D interconnected macroporous ICCN framework 104 with high electricalconductivity and high surface area. In this structure, graphene or theconducting ICCN framework 104 can act as a 3D current collector toprovide electron “superhighways” for charge storage and delivery, whilethe nanostructured MnO₂ can enable fast, reversible Faradaic reactionswith short ionic diffusion pathways. Each MnO₂ nanoparticle can beelectrically connected to the current collector so that substantiallyall of the nanoparticles can contribute to capacity with almost no“dead” mass.

FIGS. 2A-E show fabrication/synthesis and characterization oflaser-scribed graphene (LSG)/MnO₂ electrodes 205 (e.g., 3D macroporousLSG-MnO₂ electrodes, wherein a highly conductive and high-surface-area3D LSG framework was integrated with MnO₂ as schematically illustratedin FIG. 2A. The 3D LSG framework (ICCN) 203 was produced from the laserscribing 202 of graphite oxide (GO) films 201, upon which the colorchanged from golden brown to black. The LSG framework was subsequentlycoated in situ with MnO₂ using an electrochemical deposition technique204 (e.g., as described elsewhere herein).

FIG. 2B provides digital photographs showing an example of a GO filmbefore and after laser scribing. The LSG can then be loaded with MnO₂,whose amount can be controlled by adjusting the deposition time (e.g.,from about 3 minutes (min) to about 120 min). The ICCN electrode in FIG.2B turns darker in color after electrodeposition, a visual indication ofthe loading of MnO₂.

Conductivity and mass loading of the active materials can have asignificant impact on the electrochemical behavior of supercapacitorelectrodes. The mass loading of MnO₂ can be controlled by adjusting thedeposition current and deposition time. FIG. 2C shows that the MnO₂loading changes almost linearly with the deposition time at an appliedcurrent of 0.25 mA/cm² and an average deposition rate estimated to beabout 6 micrograms per minute (μg/min).

The LSG-MnO₂ electrodes can be monolithic and demonstrate superbmechanical integrity under large mechanical deformation (e.g., inaddition to interesting electrical properties). FIG. 2D shows that anLSG-MnO₂ electrode can be bent significantly without damage. Thefoldability of LSG-MnO₂ electrodes was evaluated by measuring theirelectrical resistance under successive bending cycles. In this example,the resistance varies only slightly up to a bending radius of 5.0 mm andcan be completely recovered after straightening no matter whether thebending is positive (convex) or negative (concave). As shown in FIG. 2E,after 1,000 cycles of bending and straightening at a concave bend radiusof 5.0 mm, the resistance has increased by only about 2.8%.

FIGS. 3A-G show examples of morphological and structuralcharacterization of LSG-MnO₂ electrodes. The evolution of morphologycorresponding to different deposition times was examined by scanningelectron microscopy (SEM) (FIGS. 3A-D). The SEM micrographs show thegeneral morphology and detailed microstructure of a typical sampleprepared by 120 min of deposition. MnO₂ has been uniformly coated ontothe surface of graphene throughout the entire film. In this example, theelectrodeposited MnO₂ particles show a nanoflower-shaped hierarchicalarchitecture with a clear interface between MnO₂ and the ICCN substrate.Closer inspection of the MnO₂ nanoflowers in this example shows thatthey are made up of a plurality (e.g., hundreds) of ultrathin nanoflakesthat are about 10-20 nm thick (e.g., see also FIG. 11). These nanoflakesare interconnected together to form mesoporous MnO₂ with a largeaccessible surface area (e.g., thus offering numerous electroactivesites available to the electrolyte which promotes fast surface Faradaicreactions). FIG. 3A shows an exemplary scanning electron microscopy(SEM) image of an LSG-MnO₂ electrode at low magnification, in accordancewith some embodiments.

The 3D structure of LSG-MnO₂ electrodes was further analyzed usingcross-sectional SEM (FIG. 3D). The 3D porous structure of LSG ispreserved after the deposition of MnO₂ without any agglomerations. Thegraphene surface has been uniformly coated with MnO₂ over the entirecross-section. Energy-dispersive X-ray spectroscopy (EDS), shown in FIG.3E, provides elemental maps of C, O, and Mn, confirming that ahomogeneous coating of MnO₂ throughout the 3D macroporous framework hasbeen created. X-ray photoelectron spectroscopy (XPS) data of Mn 2p andMn 3s are shown in FIGS. 3F and 3G, respectively, further confirm thechemical composition of the deposited oxide.

FIG. 11 shows an example of evolution of a surface of LSG-MnO₂ 1101. Inthis example, SEM analysis of the surface of LSG-MnO₂ electrodes shows ahomogeneous coating of the surface of graphene with MnO₂ nanoflowers1102.

Symmetric Supercapacitors

In some embodiments, symmetric supercapacitors are constructed (e.g.,fabricated or assembled) and their electrochemical performance istested. FIGS. 4A-I show examples of symmetric LSG-MnO₂ supercapacitors401 and their electrochemical performance. To test the electrochemicalperformance of LSG-MnO₂ macroporous frameworks 402, a supercapacitorpouch cell was assembled from two symmetric electrodes separated by aCelgard M824 ion porous separator and impregnated with 1.0 M Na₂SO₄electrolyte, as schematically shown in FIG. 4A.

Cells were tested by cyclic voltammetry (CV) over a wide range of scanrates from 1 to 1,000 mV/s. FIG. 4B shows examples of CV profiles for anLSG-MnO₂ sample with a deposition time of 3 min. The supercapacitorshows nearly rectangular CV profiles up to a scan rate of about 1,000mV/s (e.g., as high as 1,000 mV/s), indicating excellent charge storagecharacteristics and ultrafast response time for the electrodes.

Capacitances of the devices made with different deposition times werecalculated from CV profiles and are presented in FIG. 4C. Thecapacitance in FIG. 4C was calculated using the total volume of the cellstack (including the volume of the current collector, the activematerial, the separator, and the electrolyte), rather than a singleelectrode.

The capacitance can depend strongly on the loading amount of thepseudocapacitive component (e.g., pseudocapacitive MnO₂). In FIG. 4C,the capacitance increases significantly with deposition time from 0 toabout 960 min. For example, a stack capacitance of up to about 203 F/cm³can be achieved with the sample at a 960-minute deposition time. Thisstack capacitance translates to a volumetric capacitance of 1,136.5F/cm³ when calculated based on the volume of the active material perelectrode only. This value is much higher than the capacitance of, forexample, activated carbons (e.g., 60-80 F/cm³), carbide-derived carbons(e.g., 180 F/cm³), bare LSG (e.g., 12 F/cm³), activated microwaveexfoliated graphite oxide (MEGO) (e.g., 60 F/cm³), and liquid-mediatedchemically converted graphene (CCG) films (e.g., 263.3 F/cm³),indicating that the volumetric capacitance of carbon-based electrodescan be significantly improved by incorporating pseudocapacitivematerials (e.g., see TABLE 1). Furthermore, this value is higher thanfor MnO₂-based supercapacitors (e.g., 16.1 F/cm³ for carbonnanotube-polypyrrole-MnO₂ sponge, 130 F/cm³ for graphene-MnO₂—CNT, 246F/cm³ for CNT-MnO₂, 108 F/cm³ for mesoporous carbon/MnO₂, and 90 F/cm³for ultraporous carbon-MnO₂). Depending on the deposition time, arealcapacitances (e.g., ultrahigh areal capacitances) of up to about 0.8F/cm² per footprint of the device can be achieved (e.g., compared to,for example, areal capacitances of about 0.3 F/cm² provided bycommercial carbon supercapacitors).

TABLE 1 provides examples of electrochemical performance ofsupercapacitors comprising a variety of electrodes materials such ascarbons, polymers, MnO₂, and their hybrid materials. AN (rows 1, 2, 4and 5) refers to acetonitrile. TEABF₄ (rows 1 and 2) refers totetraethylammonium tetrafluoroborate. EMIMBF₄ (rows 3 and 5) refers to1-ethyl-3-methylimidazolium tetrafluoroborate. BMIMBF₄ (row 4) refers to1-butyl-3-methyl-imidazolium tetrafluoroborate. For the material in row10, the capacitance per footprint area in 3 electrode measurements is atleast two times the areal capacitance for 2 electrode measurements. Forthe electrode material in row 11, gravimetric capacitance is listedinstead of volumetric capacitance. The LSG-MnO₂ electrode material (row15) may be as described herein.

TABLE 1 Specific capacitance Per Footprint Cell Voltage area VolumetricElectrode Material Type window Electrolyte (mF/cm²) (F/cm³) 1 Activatedcarbons Full cell 2.7 V TEABF₄/AN ~300 60-80 2 Carbide derived carbon 32.3 V TEABF₄/AN — 180 electrode 3 LSG Full cell 4.0 V EMIMBF₄ 5.02 14.344 Activated MEGO Full cell 3.5 V BMIM- — 60 BF₄/AN 5 Liquid mediated CCGFull cell 3.5 V EMIMBF₄/AN — 263.3 6 CNT/PPy/MnO₂ Full cell 0.9 V KCl —16.1 7 Graphene/MnO₂/CNT Full cell 1.0 V 1.0M Na₂SO₄ — 130 8 CNT/MnO₂ 30.85 V  0.1M K₂SO₄ — 246 electrode 9 Meso-porous 3 0.8 V 1.0M Na₂SO₄ —108 carbon/MnO₂ electrode 10 Ultra-porous 3 0.8 V 1.0M Na₂SO₄ 1500 90Carbon/MnO₂ electrode 11 Graphene/RuO₂ 3 1.0 V 1.0M H₂SO₄ — (570 F/g)electrode 12 CNT/Co₃O₄ 3 0.5 V 2.0M KOH 30.8 30.8 electrode 13 Titaniumcarbide clay 3 0.55 V  1.0M H₂SO₄ — 910 @5 μm  electrode 534 @30 μm 355@75 μm 14 MXene/PVA 3 0.6 V 1.0M KOH — 528 electrode 15 LSG-MnO₂ Fullcell 0.9 V 1.0M Na₂SO₄ 852 1136.5 (15 μm thick film)

The contribution of the MnO₂ nanoflowers can be separated (e.g.,separately viewed/analyzed) from the average capacitance of the LSG-MnO₂electrodes. In an example, shown in FIG. 4D, specific capacitance ofMnO₂ depends on the mass of the active material, reaching a maximumvalue of about 1145 F/g (about 83% of the theoretical capacitance) at amass loading of about 13% of MnO₂. The electrode microstructure canfacilitate the transport of ions and electrons and provide abundantsurfaces for charge-transfer reactions, ensuring a greater utilizationof the active materials.

FIG. 4E shows charge-discharge curves of an LSG-MnO₂ (3 min)supercapacitor at different current densities.

MnO₂ was also electrodeposited on both CCG and gold substrates under thesame conditions as the LSG-MnO₂ macroporous electrodes. FIG. 4F providesa comparison of their electrochemical performance with LSG-MnO₂. TheCCG-MnO₂ electrode exhibits lower capacitance, and its performance fallsoff very quickly at higher charge-discharge rates. This may beattributed to the restacking of graphene sheets during the fabricationof the CCG electrodes, resulting in a significant reduction in thesurface area and eventually closing off much of the porosity. TheAu—MnO₂ electrode shows extremely low capacitance because of the limitedsurface area and structural properties (e.g., see FIG. 1A). The LSG-MnO₂shows a stack capacitance of about 50 F/cm³ that is more than four timeshigher than CCG-MnO₂ and about three orders of magnitude higher thanAu—MnO₂. The enhanced capacitance and rate capability of the LSG-MnO₂can be attributed, for example, to its improved (e.g., optimized)structure (e.g., which synergizes the effects of both effective ionmigration and high electroactive surface area, thus enabling high andreversible capacitive behavior even at high charge-discharge rates). Theimproved (e.g., optimized) ionic diffusion of the LSG network was alsoconfirmed from electrochemical impedance spectroscopy with a responsetime of about 23 milliseconds (ms) for LSG compared with about 5,952 msfor the CCG electrode(s), as shown in FIGS. 4G-H) (e.g., see also FIGS.9B, 9D, and 10).

FIG. 4I shows an example comparing capacitance of an LSG-MnO₂supercapacitor with commercially available activated carbonsupercapacitors, pseudocapacitors, and lithium-ion hybrid capacitors. Inthis example, the LSG-MnO₂ supercapacitor shows improved (e.g.,superior) volumetric capacitance and rate capability compared with thecommercially available activated carbon supercapacitors,pseudocapacitors, and lithium-ion hybrid capacitors.

The microstructure of the host graphene in a graphene/metal oxidenanocomposite can affect its electrochemical performance. The porestructure of the graphene electrode can affect the electrochemicalperformance of its composites with metal oxides.

FIGS. 9B and 9D schematically illustrate the effect of pore structure ofgraphene on its electrochemical performance for two forms of graphene ofdifferent pore structures: chemically converted graphene (CCG) films andlaser-scribed graphene (LSG) films. Schematic illustrations showstructural differences between dense CCG films FIG. 9A and porous LSGfilms FIG. 9C. Also shown in FIGS. 9B and 9D are graphs showingemergence of real (C′) and imaginary (C″) parts of volumetric stackcapacitance versus frequency for CCG and LSG electrodes (bottom). TheCCG sheets can be well connected together in a layered structure to formthe CCG electrodes. The reduced porosity and limited accessibility toelectrolyte ions can cause a slow frequency response of about 5 secondsfor CCG electrodes. LSG electrodes can have a well-defined porousstructure such that the individual graphene sheets in the LSG networkare accessible to the electrolyte, and thus exhibit a rapid frequencyresponse of 23 ms. This may cause the enhanced capacitance and ratecapability observed with the LSG-MnO₂. The improved (e.g., optimized)structure of LSG electrodes may synergize the effects of both effectiveion migration and high electroactive surface area, thus enabling, forexample, high and reversible capacitive behavior for LSG-MnO₂ even athigh charge/discharge rates.

Further understanding of the capacitive behavior of the CCG/MnO₂ andLSG-MnO₂ hybrid electrodes was obtained by conducting AC impedancemeasurements in the frequency range 1 MHz to 10 mHz. FIG. 10 showsexamples of Nyquist impedance plots of CCG/MnO₂ and LSG-MnO₂. TheLSG-MnO₂ shows better ion diffusion and smaller charge transferresistance. The experiments were carried out over a frequency range of 1MHz to 10 mHz. For each of these cells, MnO₂ was electrodeposited for120 min. The Nyquist plots consist of a spike at the low frequencyregion and a semicircle at the high frequency region. Compared withCCG/MnO₂, the LSG-MnO₂ supercapacitor shows a much smaller diameter forthe semicircle, suggesting a more efficient charge transfer on theelectrode surface. Furthermore, in the low frequency region, a morevertical straight line is observed for the porous LSG-MnO₂ electrodes,indicating faster ion diffusion and almost ideal capacitive behavior forthese electrodes. The intercept of the Nyquist curve on the real axis isabout 1.5Ω, indicating a high conductivity for the electrolyte and lowinternal resistance of the electrodes. These results show that themicrostructure of the graphene electrodes can have a strong impact onthe electrochemical performance of their composites with metal oxides.

The porosity of the LSG-MnO₂ can provide good accessibility to theelectrolyte during charge and discharge processes while at the same timestill maintaining the high packing density of the material. The highsurface area of nanostructured MnO₂ can provide more active sites forthe Faradaic reactions and shorten the ion diffusion pathways that arecrucial for realizing its full pseudocapacitance. In some examples,LSG-MnO₂ electrodes can achieve both high gravimetric capacitance andvolumetric capacitance superior to MnO₂-based pseudocapacitors andhybrid capacitors, as described in greater detail in relation to TABLE1.

Asymmetric Supercapacitors

In some embodiments, asymmetric supercapacitors are constructed (e.g.,fabricated or assembled) and their electrochemical performance istested.

Asymmetric supercapacitors can use positive and negative electrodematerials of different types that can be charged/discharged inwell-separated potential windows in the same electrolyte. Asymmetricsupercapacitors may offer high capacity via a Faradaic reaction at thepositive electrode and maintain fast charge/discharge due to the EDLmechanism at the negative electrode. The asymmetric configuration mayextend the operating voltage window of aqueous electrolytes beyond thethermodynamic limit of water (about 1.2 V) (e.g., leading tosignificantly higher specific energy than symmetric supercapacitorsusing aqueous electrolytes). In an example, asymmetric supercapacitorscan be based on carbon and NiOOH electrodes with an aqueous electrolyte.While this configuration can provide high capacitance, it can have a lowcell voltage (<1.5 V) that can be detrimental to its energy and powerperformance.

FIGS. 5A-F show examples of an asymmetric supercapacitor based onICCN-MnO₂ as positive electrode and LSG as negative electrode and itselectrochemical performance. Considering the high pseudocapacitance ofthe LSG-MnO₂ electrode and the fast charge-discharge of the double-layercapacitance of the LSG electrode, an asymmetric supercapacitor wasassembled using LSG-MnO₂ 501 as the positive and LSG 502 as the negativeelectrode, as schematically illustrated in FIG. 5A.

In this example, a charge balance between the two electrodes wasachieved by controlling the deposition time of MnO₂ at the positiveelectrode and the thickness of the ICCN film at the negative electrode.FIGS. 5B-C show electrochemical performance of an example asymmetriccell comprising a positive electrode comprising LSG-MnO₂ with 13% MnO₂mass loading (3-min deposition time). The cell exhibits an idealcapacitive behavior with nearly rectangular CV profiles and highlytriangular charge/discharge curves. The CV profiles retain theirrectangular shape without apparent distortions with increasing scanrates up to a rate (e.g., an ultrahigh rate) of 10,000 mV/s (e.g.,indicating the high rate capability of this asymmetric supercapacitor).The asymmetric cell has a wide and stable operating potential window upto about 2.0 V in aqueous electrolyte that may afford high energydensity.

FIG. 5D shows that as the MnO₂ deposition time is increased from about 3min to about 960 min, stack capacitance increases significantly fromabout 3 F/cm³ to about 76 F/cm³ (e.g., indicating that the stored energyand power can be greatly improved in the asymmetric structure). Thesecells can also retain their high capacity at faster charge and dischargerates.

The as-fabricated supercapacitor can be highly flexible and can befolded and twisted without affecting the structural integrity of thedevice or its electrochemical performance (FIG. 5E). Such a device maybe a practical energy storage system for flexible electronics.

The asymmetric supercapacitor can have a long cycle life. The asymmetricsupercapacitor can be very stable. FIG. 5F shows that the asymmetricsupercapacitor can maintain greater than about 96% of its originalcapacity after 10,000 charge-discharge cycles tested at a (e.g., high)scan rate of 1,000 millivolts per second (mV/s). The equivalent seriesresistance (ESR) of the supercapacitor was monitored during cyclingusing a Nyquist plot. A slight increase of the ESR in the first 1,000cycles was measured, with only subtle changes over the remaining cycles.

The present disclosure provides a simple technique for the fabricationof supercapacitor arrays (e.g., for high voltage applications). Thearrays can comprise interdigitated electrodes. The arrays can beintegrated with solar cells for efficient energy harvesting and storagesystems.

Three-Dimensional Interdigitated Microsupercapacitors

Microsupercapacitors with high capacity per footprint area may enableminiaturization of energy storage devices (e.g., for electronicapplications). Greater areal capacities (e.g., than currentstate-of-the-art systems with areal capacities of <11.6 mF/cm² forcarbons, <78 mF/cm² for conducting polymers, and <56.3 mF/cm² for metaloxides) may be needed. Engineering of 3D interdigitatedmicrosupercapacitors with high energy density is described, for example,in relation to FIGS. 6A-I.

FIGS. 6A-C show an example of a hybrid microsupercapacitor in which thepositive and negative electrodes are separated into a 3D interdigitatedstructure. This structure was achieved by combining the techniques of“top down” LightScribe lithography with “bottom up” selectiveelectrodeposition. First, 3D interdigitated ICCN (e.g., LSG)microelectrodes are produced by the direct writing of graphene patterns601 on GO films 602 using a consumer grade LightScribe DVD burner 603.Subsequently, MnO₂ nanoflowers 605 are selectively electrodeposited onone set of the ICCN (e.g., LSG) microelectrodes using a cell setup asdescribed elsewhere herein. The width of the microelectrodes is adjustedto match the charge between the positive and negative poles of themicrodevice.

FIG. 6D shows a digital photograph of an asymmetric microsupercapacitor605 that consists of alternating positive and negative electrodes. Thelighter microelectrodes correspond to bare ICCN (negative electrodes),whereas the other side turns darker in color after the electrodepositionof MnO₂ (positive electrodes).

FIG. 6E is an optical microscope image that shows a well-defined patternand sharp boundaries between the microelectrodes. SEM further confirmedthe conformal structure of this asymmetric microsupercapacitor.

FIG. 6F provides a magnified view at the interface between GO andgraphene showing selective electrodeposition of MnO₂ on the graphenearea only.

FIG. 6G provides examples of electrochemical characterization resultsshowing that the asymmetric microsupercapacitor provides enhancedvolumetric capacitance and rate capability compared to a sandwich-typeasymmetric supercapacitor. Symmetric hybrid microsupercapacitors canshow a similar behavior, as shown, for example, in FIGS. 6H-I, with theareal capacitance approaching about 400 mF/cm². In some examples, aninterdigitated microsupercapacitor (e.g., comprising ICCN/MnO₂) has anareal capacitance of greater than or equal to about 10 mF/cm², 50mF/cm², 100 mF/cm², 150 mF/cm², 200 mF/cm², 250 mF/cm², 300 mF/cm², 320mF/cm², 340 mF/cm², 360 mF/cm², 380 mF/cm², 400 mF/cm², 420 mF/cm², 440mF/cm², 460 mF/cm², 480 mF/cm², 500 mF/cm², 550 mF/cm², 600 mF/cm², 650mF/cm², 700 mF/cm², 750 mF/cm², 800 mF/cm², 850 mF/cm², 900 mF/cm², 950mF/cm², or 1,000 mF/cm². In some examples, an interdigitatedmicrosupercapacitor (e.g., comprising ICCN/MnO₂) has an arealcapacitance of about 300 mF/cm² to about 400 mF/cm², about 350 mF/cm² toabout 450 mF/cm², about 380 mF/cm² to about 550 mF/cm², or about 600mF/cm² to about 1,000 mF/cm². The stack capacitance significantlyimproves to about 250 F/cm³ (volumetric capacitance per electrode isabout 1197 F/cm³) which is much higher than example values for EDLC,pseudo- and hybrid microsupercapacitors: e.g., 1.3 F/cm³ for carbononions, 2.35-3.05 F/cm³ for graphene, 1.08 F/cm³ for CNT, 3.1 F/cm³ forgraphene/CNT, 180 F/cm³ (electrode) for carbide-derived carbon, 588F/cm³ for polyaniline nanofibers, 317 F/cm³ (electrode) for vanadiumdisulfide nanosheets, and 178 F/cm³ for molybdenum disulfide nanosheets(e.g., see TABLE 2).

FIG. 14A shows the full microsupercapacitor array 1401 (e.g., asfabricated by the method of FIG. 13). FIG. 14B shows an exemplarycircuit illustration of the full microsupercapacitor array 1401.

FIG. 7 shows examples of energy and power density of LSG-MnO₂-basedsupercapacitors. FIG. 7 also shows examples of energy and power densityof a number of commercially available carbon-based supercapacitors,pseudo-capacitors, hybrid supercapacitors, and Li-ion hybrid capacitors.These devices were tested under the same dynamic conditions as LSG-MnO₂.For all devices, the calculations were made based on the volume of thefull cell that includes the current collector, active material,separator, and electrolyte. The energy density of the hybrid LSG-MnO₂can vary, for example, between about 22 Wh/L and 42 Wh/L depending onthe configuration (symmetric, asymmetric and sandwich, interdigitated)and the mass loading of MnO₂. In certain embodiments, the LSG-MnO₂hybrid supercapacitors can store at least about 6 times the capacity ofstate-of-the-art commercially available EDLC carbon super-capacitors. Incertain embodiments, LSG-MnO₂ hybrid supercapacitors can be superior topseudocapacitors, hybrid supercapacitors (e.g., commercially availablehybrid supercapacitors comprising NiOOH positive electrode and activatedcarbon negative electrode, or PbO₂ positive electrode and activatedcarbon negative electrode; in such systems, the positive electrode mayhave very low electrical conductivity and thus provide little to lowpower density and/or the negative electrode activated carbon may havelimited ion diffusion rates because of its tortuous micro-porousstructure; such systems may only be built in large size spirally woundstructures and/or may not provide capability to build high-voltagecells), and/or supercapacitor-lithium-ion battery hybrid (Li-ioncapacitors). In certain embodiments, the LSG-MnO₂ supercapacitors canprovide power densities up to about 10 kW/l (e.g., about 100 timesfaster than high-power lead acid batteries and/or about 1,000 timesfaster than a lithium thin-film battery).

Supercapacitors, microsupercapacitors, and/or arrays of (micro)supercapacitors herein may maintain their capacitance at highcharge-discharge rates. For example, an array of supercapacitors (e.g.,an array of microsupercapacitors comprising ICCN/MnO₂) can maintain itscapacitance (e.g., areal capacitance) even at high charge-dischargerates. In some embodiments, a supercapacitor, microsupercapacitor and/orarray of (micro)supercapacitors herein may maintain its capacitance(e.g., areal capacitance) at a charge-discharge rate corresponding to agiven current density and/or scan rate (e.g., a high rate may correspondto a given current density and/or scan rate). In some examples, asupercapacitor, microsupercapacitor and/or array of(micro)supercapacitors herein may maintain its capacitance (e.g., arealcapacitance) at a current density of at least about 1,000 mA/cm³, 5,000mA/cm³, or 10,000 mA/cm³ (e.g., see FIG. 4F). In some examples, asupercapacitor, microsupercapacitor, and/or array of(micro)supercapacitors herein may maintain its capacitance (e.g., arealcapacitance) at a current density of up to about 1,000 mA/cm³, 5,000mA/cm³, or 10,000 mA/cm³ (e.g., see FIG. 4F). In some examples, asupercapacitor, microsupercapacitor, and/or array of (micro)supercapacitors herein may maintain its capacitance (e.g., arealcapacitance) at a scan rate of at least about 1,000 mV/s, 5,000 mV/s, or10,000 mV/s (e.g., see FIGS. 6G-I with a scan rate of, for example, upto about 10,000 mV/second; in certain embodiments, this translates to acharge time of about 0.1 second and discharge time of about 0.1 second).In some examples, a supercapacitor, microsupercapacitor and/or array of(micro) supercapacitors herein may maintain its capacitance (e.g., arealcapacitance) at a scan rate of up to about 1,000 mV/s, 5,000 mV/s, or10,000 mV/s (e.g., see FIGS. 6G-I with a scan rate of, for example, upto about 10,000 mV/second; in certain embodiments, this translates to acharge time of about 0.1 second and discharge time of about 0.1 second).The supercapacitor, microsupercapacitor, and/or array of (micro)supercapacitors may maintain its capacitance at such current densitiesin combination with one or more such scan rates. In an example, an arrayof supercapacitors maintains its capacitance per footprint (e.g., atleast about 380 mF/cm²) even at a charge-discharge rate corresponding to(i) a current density of about 10,000 mA/cm³ and/or (ii) a scan rate ofup to about 10,000 mV/s.

TABLE 2 provides examples of electrochemical performance ofmicrosupercapacitors (e.g., interdigitated microsupercapacitors).Microsupercapacitors may be, for example, interdigitated ormicro-fibers. The microsupercapacitors in table TABLE 2 can include orbe interdigitated microsupercapacitors. For example, themicrosupercapacitors in TABLE 2 can all be interdigitatedmicrosupercapacitors. Ionogel (row 3) refers toI-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionicliquid gelled with fumed silica nanopowder. The LSG-MnO₂ electrodematerial (row 12) may be as described herein.

TABLE 2 Specific capacitance Per Footprint Cell Voltage area VolumetricElectrode Material Type window Electrolyte (mF/cm²) (F/cm³) 1 Carbononions Full 3.0 V TEABF₄/PC 1.7 1.35 cell 2 Graphene Full 1.0 VPVA-H₄SO₄ 2.32 3.05 cell 3 Graphene Full 2.5 V Ionogel 1.78 2.35 cell 4Graphene-CNT carpet Full 1.0 V 1.0M Na₂SO₄ 2.16 1.08 cell 5 Graphene/CNTFull 1.0 V 3.0M KCl 5.1 3.1 cell 6 Carbide-derived Full 2.3 V TEABF₄/AN— 180 carbon cell 7 Polyaniline nanowires Full 1.0 V 1.0M H₂SO₄ — 588cell 8 Activated cabon-MnO₂ Full 1.0-1.5 V    0.2M K₂SO₄ 21.3-30 — cell9 MnO₂ Full 1.0 V 0.2M K₂SO₄ 28.3 — cell 10 VS₂ nanosheets Full 0.6 VPVA- 4.76 317 cell BMIMBF₄ 11 MoS₂ nanosheets Full 0.5 V — 8 178 cell 12LSG/MnO₂ Full 0.9 V 1.0M Na₂SO₄ 384 1136.5 cell

The present disclosure provides methods for direct fabrication ofsupercapacitor (e.g., microsupercapacitor) arrays for high voltageapplications and integrated energy storage (e.g., as described inrelation to FIGS. 8A-B).

FIG. 8A shows an array of separate electrochemical cells 801 directlyfabricated in the same plane and in one step (e.g., see also FIGS.12-16). In some embodiments, all cells (e.g., in the array) may befabricated simultaneously in one step. This configuration may show verygood control over the voltage and/or current output. In someembodiments, the array can be an asymmetric supercapacitor array. FIG.8B also shows charge-discharge curves of examples of asymmetricsupercapacitor arrays; a single device is shown for comparison. Anenlarged image and additional description of the charge-discharge datais provided in relation to FIG. 17. These arrays can offer theflexibility of controlling the output voltage and current of the array.For example, compared with a single device with an operating voltage ofabout 2 V, an array of 3 serial cells can extend the output voltage toabout 6 V, whereas the output capacity (runtime) can be increased by afactor of about 3 using an array of 3 cells connected in parallel (e.g.,see FIG. 17). By using an array of 3 strings in parallel and 3 stringsin series, the output voltage and current can both be tripled.

FIG. 8C shows that this array can be (e.g., in addition) integrated (orcoupled) with one or more solar cells for efficient solar energyharvesting and storage. The microsupercapacitor array can store theenergy produced by the solar cell during the day and release it laterwhenever needed. Such a module may be applied in a variety ofapplications, such as, for example, for self-powered street lighting.ICCN/MnO₂ (e.g., LSG-MnO₂) hybrid supercapacitors can be integrated withsolar cells (e.g., in one unit) for efficient solar energy conversionand storage. Per FIG. 8D, solar energy can be stored in an LSG-MnO₂supercapacitor pack during the day, and charged supercapacitors canprovide power after sundown. Example applications can include off-gridsolar/supercapacitor power systems.

Direct Fabrication of Hybrid Microsupercapacitor Array for High VoltageApplications

Supercapacitors may be used in a variety of applications, including, forexample, in applications where a large amount of power is needed for ashort period of time, where a very large number of charge/dischargecycles is required and/or where a longer lifetime is required.Traditional capacitors used for general electronics applications mayrange from a few volts to 1 kV. The working voltage of supercapacitorsmay be lower (e.g., very low or <3 volts). To meet the high voltagerequirements, supercapacitors can be put into a bank of cells connectedtogether in series. This can result in bulky supercapacitor moduleswhich can cause problems, for example, in applications where the totalsize of the power source is critical. The present disclosure provides anarray of separate electrochemical cells directly fabricated in the sameplane as shown, for example, in FIGS. 12-16 (e.g., to overcome theseand/or other limitations).

In some embodiments, a method to fabricate the array of separateelectrochemical cells may include a first step of fabricating an ICCNand a second step of depositing MnO₂.

Circuits can be designed using appropriate computer software and can bedirectly patterned on a graphite oxide film coated on a DVD disc. FIG.12 shows a DVD 1201 after direct writing of ICCN (e.g., LSG) patterns1202 configured (e.g., designed) to achieve symmetric and asymmetricmicrosupercapacitor arrays. The pattern can be designed, for example,with Microsoft Paint software and then directly patterned on a GO-coatedDVD disc. In an example, the device can comprise (e.g., consist of), forexample, 8 in-plane microelectrodes (4 positive and 4 negative)separated by nearly or substantially insulating GO. The distance betweenthe microelectrodes can be suitably or sufficiently short (e.g., closeenough) to keep the ion-transport pathway short. In another example,patterns may be designed to make a supercapacitor bank ofseries/parallel combinations in order to meet the voltage (series) andcurrent (parallel) requirements of the system on which they are to beintegrated (or to which they are to be coupled).

Deposition of MnO₂ nanoflowers (e.g., performed as a second step) maycomprise a deposition process that varies depending on whether asymmetric or an asymmetric array is being fabricated. Examples of suchprocesses are described in relation to FIGS. 13-14 (for an asymmetricarray) and FIG. 15 (for a symmetric array).

FIG. 13 schematically illustrates fabrication of an array of 9asymmetric cells 1301 connected in series/parallel. A plain ICCN arraycan be fabricated first (e.g., as explained in relation FIG. 12). Inthis example, the graphene pattern is designed to make an array of 9cells 1301 (3 in parallel×3 in series). This can be followed byelectrodeposition of MnO₂ 1303 in a three electrode cell asschematically illustrated in FIG. 13. For an asymmetric supercapacitor,the deposition can be controlled to go on three sets of microelectrodes(e.g., the positive electrodes) while the other three are kept intact(e.g., the negative electrodes). The deposition can be controlled suchthat, for example, electrodeposition occurs only on the three electrodesthat are electrically connected to the power source 1302 while the otherelectrodes are not connected. The MnO₂ 1303 deposition can occur on the9 cells at the same time. The fabrication of the supercapacitor arraymay therefore take approximately (e.g., almost) the same time as asingle cell without the need for further processing. In some examples,at least about 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 75, 100, 150,200, 250, 500, 750, 1,000, 2,000, 5,000, 10,000, 20,000, 50,000, 75,000,or 100,000 cells may be electrodeposited or fabricated in substantiallythe same time as a single cell fabricated by a different method. Afterthe deposition is complete, the supercapacitor array may be thoroughlywashed with de-ionized (DI) water and/or electrolyte may be added ontoeach of the cells.

FIG. 15 schematically illustrates fabrication of an array of 9 symmetricsupercapacitors 1501 connected in series and/or parallel. Thefabrication method can be similar to that of FIG. 13 except that all sixsets of microsupercapacitor electrodes act as the working electrodeduring the deposition of MnO₂ instead of the three shown in FIG. 13.

FIG. 16 shows a full set of symmetric and asymmetric supercapacitorarrays (e.g., microsupercapacitor arrays). The examples include a singleasymmetric cell 1601, an array of 3 asymmetric cells in series 1602, anarray of 3 asymmetric cells in parallel 1603 and an array of 3 series×3parallel asymmetric cells 1604 (from left to right, top), and a singlesymmetric cell 1605, an array of 3 symmetric cells in series 1606, anarray of 3 symmetric cells in parallel 1607 and an array of 3 series×3parallel symmetric cells 1608 (from left to right, bottom). A gelelectrolyte may be used to prevent leakage into other cells in thearray.

FIG. 17 shows examples of electrochemical performance of asymmetricsupercapacitor arrays (e.g., the asymmetric supercapacitor arrays inFIG. 16 (top)). Galvanostatic charge/discharge curves of asymmetricsupercapacitor arrays connected in series (“3S”) (e.g., 3 cells inseries), in parallel (“3P”) (e.g., 3 cells in parallel), and in acombination of series and parallel (“3S×3P”) (e.g., 3 series×3 parallelcells) are shown. A single device (“1 cell”) is shown for comparison.Compared with the single device with an operating voltage of about 2 V,the serial connection can extend the output voltage to about 6 V (e.g.,by a factor of about 3 at about the same output capacity (runtime)) andthe parallel connection can increase the output capacity (runtime) by afactor of about 3 (e.g., at about the same output voltage). By using acombination of series/parallel connections (e.g., 3S×3P), the outputvoltage and current can both be increased (e.g., each by a factor ofabout 3 (tripled)).

The number of cells in a high-voltage supercapacitor array can beincreased from, for example, a string of 3 cells (e.g., 3S and/or 3S×3Pin FIG. 17) to reach an operating voltage of, for example, at leastabout 100 V or other voltage(s) described elsewhere herein (e.g., inrelation to high-voltage devices). For example, a high-voltagesupercapacitor array (e.g., comprising ICCN/MnO₂) can have a voltage(e.g., operating voltage) of greater than or equal to about 5 V, 10 V,15 V, 20 V, 30 V, 40 V, 50 V, 60 V, 70 V, 80 V, 90 V, 100 V, 110 V, 120V, 130 V, 140 V, 150 V, 160 V, 170 V, 180 V, 190 V, 200 V, 210 V, 220 V,230 V, 240 V, 250 V, 260 V, 270 V, 280 V, 290 V, 300 V, 310 V, 320 V,330 V, 340 V, 350 V, 360 V, 370 V, 380 V, 390 V, 400 V, 410 V, 420 V,430 V, 440 V, 450 V, 460 V, 470 V, 480 V, 490 V, 500 V, 510 V, 520 V,530 V, 540 V, 550 V, 560 V, 570 V, 580 V, 590 V, 600 V, 650 V, 700 V,750 V, 800 V, 850 V, 900 V, 950 V, 1,000 V, 1,050 V, 1,100 V, 1,150 V,1,200 V, 1,250 V, 1,300 V, 1,350 V, 1,400 V, 1,450, or 1,500 V. Suchvoltages may be promising for a variety of applications. The voltage maybe advantageously adapted for a variety of applications.

Integration with Solar Cells

Solar power (e.g., solar cells; implementation in more energy efficientbuildings and/or smart cities) may be combined (e.g., coupled orintegrated) with an energy storage system. When combined with an energystorage system for storing energy during the day, solar cells can beused to make self-powered systems that are promising for streetlight,industrial wireless monitoring, transportation, and/or consumerelectronics applications. In some implementations, chemical batteriescan be used in such systems (e.g., due to their high energy density). Insome implementations, supercapacitors can be used in such system s(e.g., as alternatives to batteries because they can capture energy moreefficiently due to their short response time). Such modules may benefitfrom or require energy densities that are higher than the energy densityof existing supercapacitors.

The present disclosure provides supercapacitors, microsupercapacitors,and/or other devices that may be integrated with solar cells. Forexample, a microsupercapacitor array can be integrated with solar cells(e.g., for simultaneous solar energy harvesting and storage). In someembodiments, such devices (e.g., arrays of microsupercapacitors) mayachieve high voltages and/or high currents. In some embodiments, suchdevices (e.g., hybrid supercapacitors or microsupercapacitors) mayprovide higher energy density. In some embodiments, such devices (e.g.,hybrid microsupercapacitors) may provide any combination of highvoltage, high current, higher energy density, and other characteristics(e.g., as described elsewhere herein). For example, since ICCN-MnO₂(e.g., LSG-MnO₂) hybrid supercapacitors can provide higher energydensity and because they can be fabricated in arrays with high voltageand current ratings, they can be integrated with solar cells for highlyefficient energy harvesting and storage. An example of an ICCN-MnO₂microsupercapacitor array integrated with one or more solar cells may beas described in relation to FIGS. 8A-B. In some embodiments, solar cellsmay be grouped (e.g., in modules, panels and/or arrays). A solar cellarray may comprise one or more groups of solar cells (e.g., modulesand/or panels). A solar cell or a group or array of solar cells (e.g.,comprising a plurality of solar cells) may be integrated or coupled(e.g., integrated in one unit, or integrated, interconnected or coupledas separate units) with one or more supercapacitors,microsupercapacitors, and/or other devices described herein.

Supercapacitors, microsupercapacitors, and/or other devices herein maybe in electrical communication with one or more solar cells. The devices(e.g., microsupercapacitors) and/or the solar cell(s) may be configuredin a group or array. In some embodiments, an array ofmicrosupercapacitors (e.g., interdigitated microsupercapacitorscomprising at least one electrode comprising ICCN/MnO₂) may be inelectrical communication with one or more solar cells (e.g., a solarcell array). Individual solar cells (e.g., in a solar cell array) mayhave a given voltage. An array or group of such solar cells may have avoltage that depends on the interconnection (e.g., series and/orparallel) of the solar cells. The voltage of the solar cell group orarray may be matched to the voltage of the microsupercapacitor (e.g.,hybrid microsupercapacitor) array. Any aspects of the disclosuredescribed in relation to one or more solar cells may equally apply to agroup (e.g., an array, module, and/or panel) of solar cells at least insome configurations, and vice versa. In certain embodiments, a group ofsolar cells (e.g., a solar cell array) may have a voltage of greaterthan or equal to about 5 V, 10 V, 12 V, 15 V, 17 V, 20 V, 25 V, 50 V, 75V, 100 V, 125 V, 150 V, 175 V, 200 V, 250 V, 500 V, 750 V, 1,000 V,1,050 V, 1,100 V, 1,150 V, 1,200 V, 1,250 V, 1,300 V, 1,350 V, 1,400 V,1,450, or 1,500 V. In certain embodiments, the group of solar cells(e.g., a solar cell array) may comprise at least about 1, 2, 6, 8, 10,12, 14, 16, 18, 20, 25, 50, 75, 100, 150, 200, 250, 300, 350, 400, 450,500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1,000, 2,000, 3,000,4,000, 5,000, 10,000, 15,000, or more solar cells.

A solar cell (e.g., one or more solar cells in a group or array of solarcells) may be of a given type (e.g., polymer and/or transparent organicphotovoltaic cells, perovskite cells, organic cells, inorganicsemiconductor cells, multi-junction or tandem solar cells, or anycombination thereof). Solar cell(s) may be of a single junction type(e.g., comprising a single layer of light-absorbing material) ormulti-junction type (e.g., comprising multiple physical configurationsconfigured for various absorption and charge separation mechanisms). Insome embodiments, solar cell(s) can comprise (e.g., wafer-based)crystalline silicon (e.g., polysilicon or monocrystalline silicon). Insome embodiments, solar cell(s) can be thin film solar cells comprising,for example, amorphous silicon, cadmium telluride (CdTe), copper indiumgallium selenide (CIGS), silicon thin film (e.g., amorphous silicon), orgallium arsenide thin film (GaAs). In some embodiments, solar cell(s)may comprise other thin films and/or use organic materials (e.g.,organometallic compounds) as well as inorganic substances. In certainembodiments, solar cell(s) may include, for example, one or more ofperovskite solar cells, liquid ink cells (e.g., using kesterite andperovskite), cells capable of upconversion and downconversion (e.g.,comprising lanthanide-doped materials), dye-sensitized solar cells,quantum dot solar cells, organic/polymer solar cells (e.g., organicsolar cells and polymer solar cells), and adaptive cells. In someembodiments, solar cell(s) may be multi-junction or tandem cells.Further, in some embodiments, various combinations of the aforementionedsolar cell types may be implemented (e.g., in a given array).

In certain embodiments, examples of solar cells may include, but are notlimited to, for example, cells comprising conjugated polymers (e.g.,polymers containing electron conjugated units along main chain);semi-transparent, transparent, stacked or top-illuminated organicphotovoltaic cells (e.g., combining a metal nanowire network with metaloxide nanoparticles to form silver-nanowire-based composite transparentconductors that are solution-processed onto organic or polymericphotovoltaic active layers under mild processing conditions);transparent organic solar cells (e.g., visibly transparent organicphotovoltaic cells); cells comprising perovskite hybrid (e.g.,organic-inorganic perovskite) materials (e.g., comprisingorganic-inorganic thin films fabricated through a solution processfollowed by a vapor treatment); perovskite-based cells employingnon-doped small molecule hole transport materials (e.g., based onperovskite materials and using solution processable polymer materials asthe hole and electron transport layers); amorphous silicon and polymerhybrid tandem photovoltaic cells (e.g., hybrid and/or hybrid tandeminorganic-organic solar cells fabricated by, for example, roll-to-rollmanufacturing techniques); perovskite solar cells with all solutionprocessed metal oxide transporting layers; organic solar cells; tandemsolar cells; transparent solar cells; single-junction or other cellscomprising conjugated polymers with selenium substituteddiketopyrrolopyrrole unit (e.g., comprising a low-bandgap polymer);organic tandem photovoltaic devices connected by solution processedinorganic metal and metal oxide (e.g., comprising an interconnectinglayer fabricated using a metal and metal oxide nanoparticle solution);organic photovoltaic devices incorporating gold/silica core/shellnanorods into a device active layer (e.g., devices fabricated throughsolution-based processing and enabling plasmonic light trapping);multiple donor/acceptor bulk heterojunction solar cells; cells (e.g.,metal chalcogenide cells, such as, for example, CuInSe₂ cells)comprising a transparent charge collection layer (e.g., a solutionprocessable window layer comprising titanium oxide); cells comprisingelectrodes comprising a highly conductive Ag nanowire mesh compositefilm with suitable transparency and mechanical, electrical, and opticalproperties (e.g., formed by a solution-based method to improve nanowiresconnection); cells comprising solution-processed silver nanowire-indiumtin oxide nanoparticle films as a transparent conductor; cellscomprising solution processed silver nanowire composite as a transparentconductor (e.g., a silver nanowire composite coating prepared using asol-gel process as a transparent contact); copper indium gallium(di)selenide (CIGS) cells (e.g., CIGS solar cells solution-deposited byspray-coating); polarizing organic photovoltaic-based cells (e.g.,tandem solar cells); cells comprising kesterite copper zinc tinchalcogenide films (e.g., fabricated through solution synthesis anddeposition); or any combination thereof.

In some embodiments, a solar cell (e.g., one or more solar cells in agroup or array of solar cells) and/or a group or array of solar cellsmay have an efficiency (e.g., energy or power conversion efficiency) ofat least about 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%,17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, ormore. In certain embodiments, the solar cell(s) may have an efficiencyof at least about 7%, 10.5%, 13.5%, or 15%, or from about 5% to about7%.

Materials and Methods

Synthesis of LSG-MnO₂, Au/MnO₂, and CCG/MnO₂ Electrodes

In one example, the LSG framework was prepared by focusing a laser beamon a DVD disc coated with graphite oxide. In an example, the laser beamis provided by a LightScribe DVD burner (GH20LS50) and has a frequency,and power of 40 milliwatts, and 730 nanometers, respectively. First, theDVD disc is covered by a film of gold coated polyimide (AstralTechnology Unlimited, Inc.) or a sheet of polyethylene terephthalate.This was coated with a 2% GO dispersion in water using the doctor bladetechnique and left to dry for 5 hours (h) under ambient conditions. Acomputer-designed image is inscribed onto graphite oxide to make theappropriate LSG pattern. This was followed by electrodeposition of MnO₂from 0.02 M Mn(NO₃)₂ in 0.1 M NaNO₃ aqueous solution using a standardthree electrode setup, where a piece of LSG (1 cm²) is used as theworking electrode, Ag/AgCl as the reference electrode (BASi, Indiana,USA), and a platinum foil (2 cm², Sigma-Aldrich) as thecounter-electrode. The deposition was achieved by applying a constantcurrent of 250 microamperes per square centimeter (PA/cm²) for differenttime periods between 3 and 960 min. After electrodeposition, the workingelectrode was thoroughly washed with DI water to remove the excesselectrolyte and dried in an oven at 60° C. for 1 h. The amount of MnO₂deposited on the LSG framework was determined from the difference inweight of the electrode before and after electrodeposition using a highprecision microbalance with a readability of 1 microgram (μg) (MettlerToledo, MX5).

For comparison, MnO₂ was electrodeposited on other substrates such asgold-coated polyimide and graphene (CCG) paper. The gold-coatedpolyimide was obtained from Astral Technology Unlimited, Inc.(Minnesota, USA) and used without further treatment. The graphene paperwas produced as described in Li D., et al., “Processable aqueousdispersions of graphene nanosheets.” Nature Nanotechnology 3:101-105(2008), incorporated by reference herein with respect to the relevantportions therein. The gold-coated polyimide and graphene paper are cutinto rectangular strips of 1 cm² for further electrodeposition of MnO₂under the same conditions as described above.

Assembly of Sandwich-Type Hybrid Supercapacitors

Hybrid supercapacitors with sandwich structure are assembled usingelectrodes prepared in the previous section. Both symmetric andasymmetric supercapacitors are constructed. Symmetric supercapacitorsare assembled by sandwiching a Celgard M824 (Celgard, N.C., USA)separator between two identical electrodes using 1.0 M Na₂SO₄ aqueoussolution as the electrolyte. In the asymmetric structure, LSG-MnO₂ wasused as the positive electrode and LSG as the negative electrode. Forthe LSG- and CCG-based supercapacitors, stainless steel (or copper) tapewas attached to the electrodes, using silver paint, as the currentcollector. Before assembly, the electrodes are soaked in the electrolytefor 1 h to ensure proper wetting. In another embodiment, per FIGS.18A-B, the electrodes are attached using a graphene film.

Fabrication of Interdigitated Hybrid Microsupercapacitors

An example of the fabrication process of a microsupercapacitor isillustrated in FIGS. 6A-I and described below. First, LSG interdigitatedmicroelectrodes are inscribed directly on a GO film supported on agold-coated polyimide (or a polyethylene terephthalate) substrate usinga consumer grade DVD burner. Second, MnO₂ nanoflowers are grown on oneset of the interdigitated electrodes using the electrodeposition setupdescribed above. The applied current was normalized to the active LSGdeposition area at a current density of 250 μA/cm² and the mass loadingwas controlled by adjusting the deposition time. Likewise, symmetricmicrosupercapacitors based on LSG-MnO₂ as both the positive and thenegative electrodes are prepared as well. Here, the fabrication processis the same except that the two sides (instead of one side) of the bareinterdigitated LSG electrodes are connected together using copper tapeand used as the working electrode during electrodeposition. In anotherembodiment, per FIGS. 18A-B, the interdigitated LSG electrodes 1801 areconnected together using a graphene film to form a flexiblesupercapacitor array.

Characterization and Measurements

The morphology and microstructure of the different electrodes wereinvestigated by means of field emission scanning electron microscopy(JEOL 6700) equipped with energy dispersive spectroscopy (EDS) andoptical microscopy (Zeiss Axiotech 100). XPS analysis was performedusing a Kratos Axis Ultra DLD spectrometer. The thicknesses of thedifferent components of the device were measured using cross-sectionalscanning electron microscopy and a Dektak 6 profilometer. Theelectrochemical performances of the LSG-MSC supercapacitors wereinvestigated by cyclic voltammetry (CV), galvanostatic charge/dischargetests, and electrochemical impedance spectroscopy (EIS). CV testing wasperformed on a VersaSTAT3 electrochemical workstation (Princeton AppliedResearch, USA). Charge/discharge and EIS measurements were recorded on aVMP3 workstation (Bio-Logic Inc., Knoxville, Tenn.) equipped with a 10 Acurrent booster. EIS experiments were carried out over a frequency rangeof 1 megahertz (MHz) to 10 millihertz (mHz) with an amplitude of 10millivolts (mV) at open-circuit potential.

Calculations

The capacitances of the supercapacitors were calculated based on bothcyclic voltammetry (CV) profiles and galvanostatic charge/dischargecurves (CC). For the CV technique, the capacitance was calculated byintegrating the discharge current (i) vs. potential (E) plots using thefollowing equation:

$\begin{matrix}{C_{device} = \frac{\int{i\;{dV}}}{v \times \Delta\; E}} & (1)\end{matrix}$where v is the scan rate (V/s) and ΔE is the operating potential window.

The capacitance was also calculated from the charge/discharge (CC)curves at different current densities using the formula:

$\begin{matrix}{C_{device} = \frac{i_{app}}{{dE}/{dt}}} & (2)\end{matrix}$where i_(app) is the current applied (in amps, A), and dV/dt is theslope of the discharge curve (in volts per second, V/s). Specificcapacitances were calculated based on the area and the volume of thedevice stack according to the following equations:

$\begin{matrix}{{{Areal}\mspace{14mu}{capacitance}\mspace{14mu}\left( C_{A} \right)} = \frac{C_{device}}{A}} & (3) \\{{{Volumetric}\mspace{14mu}{stack}\mspace{14mu}{capacitance}\mspace{14mu}\left( C_{v} \right)} = \frac{C_{device}}{V}} & (4)\end{matrix}$where A and V refer to the area (cm²) and the volume (cm³) of thedevice, respectively. The stack capacitances (F/cm³) were calculatedtaking into account the volume of the device stack. This includes theactive material, the current collector, and the separator withelectrolyte.

The energy density of each device was obtained from the formula given inEquation (5):

$\begin{matrix}{E = {\frac{1000}{2 \times 3600}C_{v}\Delta\; E^{2}}} & (5)\end{matrix}$where E is the energy density in Wh/L, C, is the volumetric stackcapacitance obtained from galvanostatic charge/discharge curves usingEquation (3) in F/cm³ and ΔE is the operating voltage window in volts.

The power density of each device was calculated using the equation:

$\begin{matrix}{P = \frac{E}{t}} & (6)\end{matrix}$where P is the power density in W/L and t is the discharge time inhours.

Volumetric capacitance based on the volume of the active material onlywas calculated using the following equations:

Volumetric capacitance of the device,

$\begin{matrix}{C_{v{({device})}} = \frac{C_{device}}{V}} & (7)\end{matrix}$where V is the volume of the active material on both electrodes;

Volumetric capacitance per electrode,C _(v(electrode))=4×C _(v(device))  (8)

The specific capacitance contributed by MnO₂ alone was calculated bysubtracting the charge of the bare LSG framework according to theequation C_(s,MnO2)=(Q_(LSG/MnO2)−Q_(LSG))/(ΔV×m_(MnO2)), where Q is thevoltammetric charge, ΔV is the operating potential window and m is themass.

Asymmetric supercapacitors may be configured such that there is a chargebalance between the positive and negative electrodes (e.g., to achieveoptimal performance with asymmetric supercapacitors). The charge storedby each electrode depends on its volumetric capacitance(C_(v(electrode))), volume of the electrode (V), and the potentialwindow in which the material operates (ΔE).q=C _(v(electrode)) ×V×ΔE  (9)

Charge balance can be attained when the following conditions aresatisfied:

$\begin{matrix}{q_{+} = q_{-}} & (10) \\{\frac{V_{+}}{V_{-}} = \frac{C_{{v{({electrode})}} -} \times \Delta\; E_{-}}{C_{{v{({electrode})}} +} \times \Delta\; E_{+}}} & (11)\end{matrix}$

The charge balance was achieved by adjusting the thickness of thepositive and negative electrodes.

Comparison with Commercial Energy Storage Systems

The performance of a wide range of commercially available energy storagesystems was tested for comparison with LSG-MnO₂ hybrid supercapacitorsand microsupercapacitors. The tested energy storage systems include, forexample, activated carbon (AC) supercapacitors, a pseudocapacitor (2.6V, 35 mF), a battery-supercapacitor hybrid (lithium ion capacitor) (2.3V, 220 F), an aluminum electrolytic capacitor (3 V, 300 microfarads(μF)) and a lithium thin-film battery (4 V/500 microampere-hours (μAh)).Activated carbon supercapacitors of varying sizes were tested: smallsize (2.7 V, 0.05 F), medium size (2.7 V, 10 F), and large size (2.7 V,350 F). The activated carbon large cell (2.7 V, 350 F) was tested at alower current density of 160 milliamps per cubic centimeter (mA/cm³) duea 10 A maximum current limitation of measuring equipment. The deviceswere tested under the same dynamic conditions as the LSG-MnO₂ hybridsupercapacitors and microsupercapacitors.

XPS Analysis

XPS was used to analyze the chemical composition and the oxidation stateof Mn in LSG-MnO₂ electrodes. The Mn 2p and Mn 3s spectra are presentedin FIGS. 3F-G. The peaks of Mn 2p_(3/2) and Mn 2p_(1/2) are located at642.1 electronvolts (eV) and 653.9 eV, respectively, with a spin energyseparation of 11.6 eV. The peak separation of the Mn 3s doublet can berelated to the oxidation state of Mn in manganese oxides (e.g., 5.79 eVfor MnO, 5.50 eV for Mn₃O₄, 5.41 eV for Mn₂O₃ and 4.78 eV for MnO₂). Theas-prepared LSG-MnO₂ showed a separation energy of 4.8 eV for the Mn 3sdoublet (FIG. 3G), suggesting that the oxide is MnO₂, which was furtherconfirmed from the O 1s spectrum.

Systems, devices, and methods herein may be adapted to other activematerials. Such embodiments may enable, for example, fabrication ofbatteries comprising a plurality of interconnected battery cells, orother devices (e.g., photovoltaics, thermoelectrics or fuel cells)comprising cells with asymmetric electrodes.

Systems, devices, and methods herein (e.g., supercapacitors) may be usedin a variety of applications, including but not limited to, for example,hybrid and electric vehicles, consumer electronics, military and spaceapplications, and/or portable applications (e.g., smartphones, tablets,computers, etc.). Energy storage devices (e.g., high-voltage devices)herein can be compact, reliable, energy dense, charge quickly, possessboth long cycle life and calendar life, or any combination thereof. Insome cases, supercapacitors may be used to replace or complementbatteries. For example, the hybrid supercapacitors herein may store asmuch charge as a lead acid battery, yet be recharged in seconds comparedwith hours for conventional batteries.

While preferable embodiments of the present invention have been shownand described herein, it will be obvious to those skilled in the artthat such embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. An electrochemical system comprising: a planararray of interconnected electrochemical cells; wherein eachelectrochemical cell comprises at least two electrodes, wherein eachelectrode comprises a charge storing active material comprising athree-dimensional interconnected corrugated carbon-based network (ICCN)comprising a plurality of expanded and interconnected carbon layers andhaving a plurality of pores, and wherein at least one electrode furthercomprises pseudocapacitive nanostructures electrodeposited within atleast a portion of the plurality of pores; and a current collectorcoupled to the planar array of interconnected electrochemical cells. 2.The electrochemical system of claim 1, wherein the pseudocapacitivenanostructures comprise MnO₂, RuO₂, Co₃O₄, NiO, Fe₂O₃, CuO, MoO₃, V₂O₅,Ni(OH)₂, or any combination thereof.
 3. The electrochemical system ofclaim 1, wherein the planar array of interconnected electrochemicalcells is arranged in an interdigitated structure.
 4. The electrochemicalsystem of claim 1, further comprising an electrolyte disposed betweenthe at least two electrodes.
 5. The electrochemical system of claim 1,wherein at least one electrochemical cell is capable of outputting avoltage of at least about 5 volts.
 6. The electrochemical system ofclaim 1, wherein the electrochemical system is capable of outputting avoltage of at least 100 volts.
 7. The electrochemical system of claim 1,wherein at least one electrochemical cell has an energy density of atleast about 22 watt-hours per liter (Wh/L).
 8. The electrochemicalsystem of claim 1, wherein the planar array of interconnectedelectrochemical cells has a capacitance per footprint of at least about380 millifarads per square centimeter (mF/cm²).
 9. The electrochemicalsystem of claim 1, wherein the planar array of interconnectedelectrochemical cells has a volumetric capacitance of at least about1,100 farads per cubic centimeter (F/cm³).
 10. The electrochemicalsystem of claim 1, comprising one or more positive electrodes having afirst mass loading of the pseudocapacitive nanostructures and one ormore negative electrodes having a second mass loading of thepseudocapacitive nanostructures, wherein the first mass loading isgreater than the second mass loading.
 11. The electrochemical system ofclaim 1, wherein the pseudocapacitive nanostructures comprise apseudocapacitive nanoflower, a pseudocapacitive nanoflake, apseudocapacitive nanorod, a pseudocapacitive nanowire, or anycombination thereof.
 12. A method for fabricating an electrochemicalsystem, comprising: forming a carbonaceous film on a current collector;forming a charge storing active material comprising a three-dimensionalinterconnected corrugated carbon-based network (ICCN) having a pluralityof pores from the carbonaceous film; patterning the three-dimensionalinterconnected corrugated carbon-based network (ICCN) to form an arrayof two or more cells, wherein each cell comprises at least twoelectrodes; and electrodepositing pseudocapacitive nanostructures withinat least a portion of the plurality of pores.
 13. The method of claim12, wherein the carbonaceous film comprises graphene oxide (GO).
 14. Themethod of claim 12, wherein said forming the charge storing activematerial comprising the three-dimensional interconnected corrugatedcarbon-based network (ICCN) from the carbonaceous film comprises lightscribing.
 15. The method of claim 12, wherein said patterning thethree-dimensional interconnected corrugated carbon-based network (ICCN)comprises light scribing.
 16. The method of claim 12, wherein saidpatterning the three-dimensional interconnected corrugated carbon-basednetwork (ICCN) forms two or more interdigitated electrodes.
 17. Themethod of claim 12, wherein the array of two or more cells is a planararray.
 18. The method of claim 12, wherein the pseudocapacitivenanostructures comprise MnO₂, RuO₂, Co₃O₄, NiO, Fe₂O₃, CuO, MoO₃, V₂O₅,Ni(OH)₂, or any combination thereof.
 19. The method of claim 12, furthercomprising depositing an electrolyte on the three-dimensionalinterconnected corrugated carbon-based network (ICCN).
 20. The method ofclaim 12, further comprising connecting two or more cells within thearray.